Peel onions and garlic and cut into fine cubes. Wash and peel carrots and celery and cut into fine cubes. Clean, halve, wash and finely dice the leek.
Heat the oil in a frying pan. Fry the minced meat over medium heat while turning. Add the diced vegetables, onion and garlic, sweat them and season with salt, pepper and sugar. Add tomatoes and simmer for about 20 minutes at low heat.
Season with salt, pepper and sugar. Prepare gnocchi in boiling salted water according to package instructions, drain and add to the sauce. Arrange on plates and garnish with a few leaves of basil.