Peel and finely dice the onions and garlic. Press the sausage out of the skin in small balls. Heat the oil in a pan, add the sausage balls and fry them for 3-4 minutes, turning them over.
Sauté onions and garlic in the frying fat. Add tomato paste, herbs and sugar and sweat. Deglaze with tomatoes and stock. Season with salt, pepper and chili. Bring to the boil, add peas and simmer for about 8 minutes.
Meanwhile, prepare the pasta in boiling salted water according to the instructions on the packet. 3 minutes before the end of the cooking time, add sausage balls to the tomato sauce and heat up with it. Wash the thyme, shake dry and remove leaves from some stalks.
Drain the mozzarella and pluck into pieces. Pour the pasta into a sieve, drain well and mix into the sauce with the plucked thyme leaves. Season again with salt, pepper, sugar and chili.
Arrange on plates. Sprinkle immediately with mozzarella and garnish with remaining thyme stems.