Wash the potatoes, cut into 4mm slices and boil in salted water for 4 to 5 minutes. Drain carefully and allow to dry. The potato slices should not yet be fully cooked.
Heat the oil in an ovenproof pan and fry the onion, garlic and carrots with the bay leaf until the onion is translucent. Add the minced meat and fry for 4 minutes. Add the tomato puree and tinned tomatoes.
Dissolve the vegetable stock and flour in the boiling water and add to the tomato sauce. Season to taste with herbes de Provence, salt and pepper and simmer. Add the peas and mix well.
Remove the bay leaves from the pan, toss the sauce and arrange the slices of potato on top.
Brush with the sour cream and sprinkle the mozzarella on top. Bake in the middle of the oven for 25-30 minutes until golden brown. If the crust becomes too brown and the potatoes are not cooked enough, cover with aluminium foil.