400g fluffy potatoes, e.g Maris Pipers, sliced thinly, lengthwise
2 tablespoons olive oil
1 medium white onion, peeled and chopped
120g button mushrooms, sliced
1 garlic clove, peeled and chopped
500g minced beef
1 x 400g can chopped tomatoes
1 tablespoon ground cinnamon
2 teaspoons ground allspice powder
1 tablespoon tomato purée
For the white sauce (Béchamel sauce):
50g butter
50g flour
400ml milk
1 bay leaf
Pinch ground nutmeg