Mary Berry served up a potato, leek, cheese pie with French Dijon mustard, flaky pastry and a vegetarian filling on Mary Berry Everyday.

The ingredients for the flaky pastry are: 125g butter, frozen for 1 hour, 125g hard vegetable fat, such as Trex, frozen for 1 hour, 350g plain flour, plus extra for dusting and 1 free-range egg, beaten for egg wash.

For the pie filling: 60g butter, 2 small leeks, thinly sliced, 1 onion, thinly sliced, 450g potatoes, cut into 2cm cubes, 600ml full-fat milk, 50g plain flour, 1 tbsp Dijon mustard, 1 tbsp chopped fresh thyme, 50g mature Cheddar, finely grated, 50g Parmesan or vegetarian hard cheese, finely grated, salt and freshly ground black pepper.

The recipe is available in Mary’s book titled: Mary Berry Everyday – available at Amazon now.