Brown the minced beef, onion and mushrooms in a saucepan. Stir in the flour and tomato purée and blend in the stock. Add 2 tsp Herbes de Provence, Garlic Granules, Salt and Black Pepper to taste. Cover and simmer gently for 20 minutes.
Meanwhile, cook the spinach according to packet instructions. Drain thoroughly. Place the minced beef mixture in a deep ovenproof dish and cover with the cooked spinach. Add a pinch of Black Pepper and ½ tsp Herbes de Provence to the soured cream and spread over the spinach.
Sprinkle with grated cheese and place under a hot grill for 2-3 minutes or until golden.