Leftover Beef Wellington Sandwich

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This sandwich is the best way to serve leftover beef wellington! Inside a toasted bun, there’s garlic mushrooms, gravy, béarnaise sauce & leftover beef.

leftover beef wellington sandwich

This isn’t your everyday sort of sandwich! This is a leftover beef wellington sandwich, which is designed to use up those end slices that tend to be cooked at bit more. We’ll be reheating these leftovers in gravy, so they’ll be extra delicious & incredibly tender!

To make this sandwich, we take a homemade potato bun and fill it with fried garlic mushrooms, a thick slice of leftover beef wellington, red wine gravy & a homemade bearnaise sauce. This one’s proper tasty!

If you’re looking for more lunch inspiration, take a look at our ever growing collection of lunch recipes. There’s something for everyone here, from vibrant salads, to next level sandwiches & homemade scotch eggs.

Components Of This Sandwich

This sandwich is designed to make use of any leftovers that you may have from making & serving your wellington. To make this sandwich, I used mushrooms that I had leftover from when I made the duxelles & homemade red wine gravy, which I served with my beef wellington…

Leftover Beef Wellington

The main component of this sandwich! We’re using half a slice of beef wellington in each bun, which we’re reheating in gravy to keep it nice & tender. I like to use the end slices of wellington for these sandwiches, as these tend to be cooked a bit more than the centre.

If you didn’t have any beef wellington, this sandwich will be just as good with slices of steak. Ribeye, sirloin or fillet would work great!

Red Wine Gravy

I served my beef wellington with some homemade red wine gravy, so this is what I used to reheat my beef in. If you don’t have any homemade gravy, you can use ready made gravy or granules mixed with hot water (like bisto) instead. I wouldn’t reheating the slices of wellington without any sauce, as it tends to dry out in the oven.

Béarnaise Sauce

This is a classic steak sauce that works fantastically with all types of beef! To make bearnaise sauce, we make whisk egg yolks & vinegar over a bain marie until thick enough to coat the back of a spoon then we whisk in melted butter, to emulisfy the sauce. To this, we add a splash of lemon juice & plenty of finely chopped tarragon then we season to taste, with salt & pepper.

Garlic Mushrooms

Another classic steak garnish! To make these, we thinly slice some mushrooms then pan fry them until they’re crisp & golden. Then to finish, we add in plenty of grated garlic & a chunk of butter then cook for another minute.

Toasted Burger Bun

I used my potato burger buns for this sandwich but any good burger bun will do the trick! I’d definitely recommend toasting the burger buns, to prevent them going soggy (from the gravy & bearnaise).

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Leftover Beef Wellington Sandwich

This sandwich is the best way to serve leftover beef wellington! Inside a toasted bun, there's garlic mushrooms, gravy, béarnaise sauce & leftover beef.
Prep Time20 minutes
Cook Time15 minutes
Total Time35 minutes
Course: Dinner, Lunch
Cuisine: British
Servings: 4 Sandwiches
Author: Ben Racey


  • Large Frying Pan
  • Ovenproof Dish
  • Mixing Bowl
  • Saucepan


  • 4 Burger Buns (See Notes)

Beef Wellington

  • 2 Thick Slices Of Leftover Beef Wellington (See Notes)
  • 300 g Gravy

Béarnaise Sauce

  • 100 g Unsalted Butter
  • ½ tbsp White Wine Vinegar
  • 25 g Egg Yolks
  • ½ tbsp Lemon Juice
  • 1 tbsp Finely Chopped Tarragon

Garlic Mushrooms

  • 250 g Chestnut Mushrooms
  • 1 tbsp Vegetable Oil
  • 3 Garlic Cloves
  • A Knob Of Butter


Beef Wellington

  • Preheat an oven to 180°c/160°c fan (356°f/320°f).
  • Cut each slice of beef wellington in half then place into an ovenproof dish. Spoon gravy over each slice then cover the dish with foil. Bake in the oven for 10-15 minutes, until hot.

Béarnaise Sauce

  • Place the butter into small saucepan then cook over a low heat, until melted. Pour into a jug then set aside.
  • Next, place the vinegar & yolks into a heatproof mixing bowl, whisk to combine then set over a pan of barely simmering water. Make sure the bottom of the bowl isn't touching the water.
  • Gently cook the egg yolks, whisking constantly until the mix is thick enough to coat the back of a spoon. This will take 2-3 minutes.
  • Take the bowl off the heat then slowly pour in the melted butter, whisking constantly, to emulsify. If the sauce seems a little thick, whisk in some of the milk solids from the bottom of the jug as well.
  • Whisk the lemon juice & chopped tarragon into the sauce then season with salt & pepper, to taste. Set aside for now.
    If the béarnaise sauce has thickened up too much when you go to serve it, whisk in a splash of warm water.

Garlic Mushrooms

  • Place a large frying pan over a high heat. If you'd like to toast your burger buns, cut them in half & toast them now, in the dry frying pan.
  • Next, add the tbsp of veg oil into the pan & leave to get smoking hot. In the meantime, thinly slice the mushrooms & grate the garlic. Set the garlic to one side.
  • Add the mushrooms into the pan, season with salt then fry until golden & crisp, tossing the pan regularly.
  • Add the garlic & butter to the mushrooms, cook for another minute then season with freshly cracked black pepper.

Assembling The Sandwich

  • Divide the garlic mushrooms between each bun then top with the warm beef wellington, the gravy & a generous amount of béarnaise sauce. Place the top part of each bun on top then serve straight away.


1. Cooking On An Aga – Reheat the beef wellington in the baking oven, on the bottom set of runners. Use the simmering plate when making the bearnaise & fry the mushrooms using the boiling plate.
2. Beef Wellington – You’ll need two thick slices of beef wellington for this sandwich. There’s half a slice in each bun! I’d recommend using leftovers from our beef wellington recipe
3. Burger Buns – I used my potato burger buns for this sandwich but any good burger bun will work. 
4. Béarnaise Béarnaise sauce is best served warm, so can’t really be made in advance. Feel free to add in more tarragon if you’d prefer a stronger flavour.
5. Gravy – I reheated my beef wellington with my homemade red wine gravy. Feel free to use a different gravy if you’d prefer.  
6. Mushrooms – Pretty much any type of mushroom can be used for this sandwich. I used chestnut mushrooms but button or portobello would be some other good options.

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One Comment

  1. I haven’t made this or the Wellington yet but this should be illegal 🤤!
    Thanks for all the amazing recipes!

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