Make the sauce:
Heat olive oil in a skillet over medium heat. Sauté onion, garlic, and celery for 3-4 minutes until soft. Add ground meat, cook for 5-7 minutes, breaking up clumps, until browned. Stir in tomato sauce, salt, pepper, and herbs. Simmer for 10 minutes on low heat.
Assemble the dish:
Preheat oven to 180°C (350°F). In a small baking dish (about 20x20 cm or 8x8 inches), spread the meat sauce evenly. Top with gnocchi (or pasta) and sprinkle with grated mozzarella.
Bake:
Cover with foil or parchment paper and bake for 20 minutes. Remove cover and bake for another 10 minutes until the cheese is golden.
Serve:
Serve hot, garnished with fresh herbs (optional).