Roasted Garlic Mashed Potato Casserole
Creamy mashed potato, flavoured with roasted garlic & topped with cheese, bacon & breadcrumbs then baked until crisp. This is an indulgent side dish that’s perfect for Thanksgiving.
Mashed potatoes casserole is a next level side dish to serve on Thanksgiving or with a roast dinner, steak or fried chicken! It’s incredibly easy to prepare, is absolutely jam packed full of flavour & can even be made several days ahead of time.
So the main component of a mashed potato casserole is of course mashed potato. This isn’t just any old mashed potato though! It’s flavoured with a whole bulb of roasted garlic, loads of grated cheese, sour cream, double cream & fresh herbs. Then it’s topped with more cheese, crispy bacon & breadcrumbs then baked until crisp & golden. If you like creamy mashed potato & crispy cheese and bacon, this is the side for you!
For more side dishes to try, take a look at our collection of sides! And for a main course to serve with this roasted garlic mashed potato casserole, check out our ever growing collection of dinner recipes.
What Is A Mashed Potato Casserole
Mashed potato casserole is a classic Thanksgiving side dish that’s made by topping mashed potato with cheese & breadcrumbs (and sometimes crispy bacon!) then baking in the oven until crisp & golden. This isn’t just regular mashed potato though! It’s made with sour cream, double cream & plenty of grated cheese, for an extra creamy texture & loads of flavour!
What You’ll Need
- Potatoes – I used Maris Piper potatoes for my mashed potato casserole but other floury varieties like Russets, King Edwards & Yukon Golds will work as well.
- Garlic – You’ll need a whole bulb of garlic for this recipe. We’re going to be roasting this whole then mashing the cloves into the potatoes.
- Milk & Cream – We’re adding whole milk & double cream to our mash, for a creamier texture! For extra flavour, we’re infusing them with rosemary, thyme & grated nutmeg.
- Sour Cream – For an even creamier mashed potato, we’re also adding sour cream into it! You’ll notice that we’re not using butter as well. This is because of all the added milk, cream & cheese! However, feel free to add in a small amount for some added flavour.
- Cheese – Our mashed potato casserole has cheese mixed through the mash & baked on top, for a crispy topping! I used a mix of mature cheddar & Red Leicester but feel free to use different cheeses if you’d prefer. Parmesan, mozzarella, Gruyere & Monterey Jack are all good options.
- Bacon – This casserole is topped with crispy bacon lardons. You’ll need streaky bacon for this & you can use either smoked or unsmoked.
- Breadcrumbs – Sprinkled on top of the mashed potato before baking, to give the casserole a crunchy topping! Panko breadcrumbs work best.
How To Make Roasted Garlic Mashed Potato Casserole
The process behind making a roasted garlic mashed potato casserole is simple! You make regular mashed potatoes then add in sour cream, grated cheese, roasted garlic, double cream & milk. The mash gets placed into a baking dish, topped with more grated cheese, breadcrumbs & crispy bacon then baked until crisp & golden.
For a fluffier, lighter mashed potato with more flavour, we’re going to be baking the potatoes instead of boiling them. At the same time, we’re going to be roasting a bulb of garlic, to mash up & fold through the mash. You can boil potatoes for mash but you’ll get a better texture & flavour by baking them. Plus, we need the oven for the garlic so why make extra work for ourselves?!
- Baked Potatoes
First, we need to bake whole potatoes in the oven (like a baked potato) until the potato inside is tender; use a knife to test this. To cook, we poke the potatoes with a fork, place onto a baking tray then bake at 200°c/392°f for around an hour. - Roasted Garlic
We’re going to be roasting the garlic in the oven at the same time as the potatoes. This won’t take as long though, so you’ll need to check it after around 30 minutes. To roast the garlic, we cut a small amount off the top of the bulb to expose the garlic inside then drizzle with oil, wrap in foil, place onto the tray of potatoes then roast. - Mashed Potatoes
Once the potatoes & garlic are cooked, we need to let them both cool slightly (around 15 minutes or so) before mashing; they should be warm but not piping hot. Next, we scoop out the potato flesh & squeeze the garlic out of the skins then use a potato ricer to mash both into a large mixing bowl. - Mix Ins
Now to flavour the mash. To do this, we’re going to warm milk & cream up in a pan with fresh herbs & nutmeg then strain into the mash once infused. We’re also going to add in sour cream, grated cheese and salt & pepper then mix until just combined. - Crispy Bacon Breadcrumbs
Our casserole is topped with crispy bacon breadcrumbs! These are really simple to make; we fry (or grill) streaky bacon until crispy, drain on kitchen paper then chop into bitesize pieces & mix with panko breadcrumbs. - Assembly
Once all of the components are ready, we spoon the mash into a buttered baking dish, top with the bacon breadcrumbs & more grated cheese. I used a 10″ round baking dish but you could use a square or rectangle dish instead if you like.
See the “FAQ” section for make ahead instructions! - Baking
To cook the mashed potato casserole, we bake it at 200°c/392°f for 20-25 minutes until the top is crisp & golden. - Serving
Once cooked, we top the casserole with a sprinkle of finely chopped chives then serve!
What To Serve Mashed Potato Casserole With
Mashed potato casserole is a classic side dish to serve at Thanksgiving, alongside your roasted turkey, prime rib or baked ham! However, mashed potato casserole goes really well with braised meats & stews, steaks, sausages & as part of a roast dinner. Or you can eat it on its’ own!
Frequently Asked Questions
To cook mashed potato casserole in an Aga, bake the potatoes & garlic in the roasting oven, on the bottom set of runners & use the simmering plate to warm the cream. The mashed potato casserole can be baked on the bottom set of runners in the roasting oven or on the second from top set of runners in the baking oven.
A floury variety of potato is best for mashed potato casserole as they have a lighter, fluffier texture once cooked & mashed. I recommend using Maris Pipers but Russets, King Edwards or Yukon Golds will all work as well.
Yes, mashed potato casserole is a fantastic side dish to make ahead of time! To make mashed potato casserole in advance, make the mashed potato & place into a baking dish then leave to cool, cover in clingfilm then store in the fridge for up to 3 days. When you’re ready to bake the casserole, let it sit out of the fridge for an hour before baking.
Mashed potato casserole will keep in the fridge for up to 3 days before being baked & it’s best to wrap it in clingfilm to keep it fresh. Mashed potato casserole is best eaten straight after baking but leftovers will keep for a day or two & can be reheated in the oven, covered in foil if the top starts to brown too much.
To avoid gluey mashed potatoes, it’s important not to overwork the potatoes as you mash them. The best way to mash potatoes is with a potato ricer or a masher. Using a blender, food processor or mixer will over work the potatoes, making the mash gummy.
More Side Dishes To Try!
- Garlic & Parmesan Creamed Corn
- Guinness & Bone Marrow Gravy
- Goose Fat Roasted Crushed New Potatoes
- Honey Butter Buttermilk Cornbread
- Fondant Potatoes
- Dauphinoise Potatoes
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Roasted Garlic Mashed Potato Casserole
Equipment
- Large Baking Tray
- Potato Ricer
- Mixing Bowl
- 10" Round Baking Dish (Or A Similar Size Square/Rectangle One)
- Cheese Grater
Ingredients
Baked Potatoes & Garlic
- 2.5 kg Maris Piper Potatoes (See Notes)
- 1 Garlic Bulb
- 2 tsp Vegetable Oil
Infused Cream
- 250 g Double Cream
- 200 g Whole Milk
- A Few Sprigs Of Rosemary
- A Few Sprigs Of Thyme
- Nutmeg (To Taste)
Mashed Potato Casserole
- 250 g Sour Cream
- 100 g Mature Cheddar
- 100 g Red Leicester
- 40 g Panko Breadcrumbs
- 6 Rashers Of Streaky Bacon (Smoked Or Unsmoked)
- Finely Chopped Chives (To Serve)
Instructions
Roasted Potatoes & Garlic
- Preheat an oven to 200°c/180°c fan (392°f/356°f).
- Prick the potatoes all over with a fork then place onto a large baking tray.
- Next, cut a small amount off the top of the garlic bulb, to expose the garlic inside then place onto a piece of foil, drizzle over the veg oil then wrap up in the foil.
- Place the foil wrapped garlic onto the tray of potatoes then place into the preheated oven. Bake until the potatoes are tender & the garlic is soft. This will take around 1 hour.Give the potatoes a poke with a small knife. If it slides into the potato with little to no resistance, they're cooked. The garlic will take 45 minutes – 1 hour to cook so might be done before the potatoes.
- Once cooked, let the potatoes & garlic cool for 15-20 minutes before mashing. The potatoes need to be warm when we mash them but not too hot, as they'll be difficult to handle.We'll be baking the casserole at the same oven temperature so you can leave it turned on or preheat it again if you're not baking it straight away!
Crispy Bacon
- Whist your potatoes are cooking, fry the streaky bacon until golden & crispy. You can do this in a frying pan over a medium heat or under a grill. It's up to you!
- Once cooked, let the bacon drain on a plate lined with kitchen paper.
Infused Cream
- Whilst your potatoes are cooling, place the cream, milk, herbs & nutmeg into a saucepan, season well with salt & pepper then warm over a low heat until steaming hot. Set to one side & leave to infuse until you mash the potatoes.
Mashed Potatoes
- Grate both of the cheeses, place into a mixing bowl & mix to combine. Set aside for now.
- Next, cut the potatoes in half then use a spoon to scoop out the flesh. Use a potato ricer to mash the potatoes into a large mixing bowl.If you haven't got a ricer, scoop the potato out of the skins, place into a mixing bowl then use a potato masher to mash once you've added in the cream & milk.
- Squeeze the roasted garlic cloves out of their skins then use the potato ricer to mash into the potatoes.
- Pour the infused cream into the potatoes through a sieve then add in the sour cream & half of the grated cheese. Mix to combine then season to taste with more salt & pepper as needed.
- Transfer the mashed potatoes into a large baking dish that has been lightly greased with butter, spreading it out into an even layer. I like to place the dish onto a baking tray, as this makes it easier to take out of the oven!I used a 10" round baking dish.
- Next, chop the crispy bacon into small, bitesize pieces, place into a small mixing bowl with the breadcrumbs then mix to combine.
- Sprinkle the bacon & breadcrumbs over the top of the mashed potatoes then sprinkle over the rest of the grated cheese. Bake in the preheated oven for 20-25 minutes until the top is crisp & golden and the mash is piping hot.
- Once cooked, top the casserole with a sprinkle of finely chopped chives then serve!
