In a bowl, combine cornflour, semolina & a pinch of salt and pepper.
Return the potatoes to the saucepan they were cooked in. Sprinkle over the semolina & cornflour, place the lid back on the pan & give the pan a good shake.
Take the roasting tray out of the oven & using a pair of tongs, carefully transfer the potatoes into the fat, turning them so that they completely coated in fat.
Add the crushed garlic into the tray then return to the oven & cook for 40 minutes, turning halfway through.
Next, melt the butter (on the stove or in a microwave) then stir in the chopped herbs.
Take the potatoes out of the oven then pour the herb butter all over. Season the potatoes with salt & pepper, give the tray a good shake/stir then return to the oven & cook for another 10 minutes. Once cooked, transfer the roast potatoes to a serving dish & finish with a sprinkling of sea salt.