Bring about 2 - 3 liters of water with plenty of salt to a boil in a large saucepan. Cook the spaghetti until al dente.
Heat the olive oil in a large pan, sauté the spring onions cut into rings and the chilli pepper cut into rings. Halve the cherry tomatoes and add to the pan after 3 - 5 minutes, sauté briefly.
Roughly cut the basil into strips, leaving a few small leaves for decoration later. Dice the mozzarella.
Add the drained spaghetti to the pan with the onion rings and tomatoes. Put the basil strips on top, mix briefly and leave to stand for approx. 2 minutes. Then pour the mozzarella cubes over it and fold in carefully. Season with pepper from the mill.
Spread the spaghetti on plates and decorate with the leftover basil leaves.