Peel and finely chop the onion and garlic. Sauté them in butter until they become tender.
Stir in the tomatoes (previously cut into small pieces), the ground meat, the flour, the herbes de Provence, and a little salt and pepper. Mix well and let it cook.
Once the mixture is cooked, remove it from the heat, then add the egg yolk and a small amount of Parmesan cheese. Mix thoroughly until the mixture is smooth.
Preheat the oven to 200°C. Spread the meat mixture evenly over the bottom of a baking dish. Prepare the mashed potatoes and spread them evenly over the meat. Sprinkle with grated cheese and bake until the top is golden brown.
