Cook the pasta in salted water. Preheat the oven to 200 ° C top / bottom heat or 175 ° C circulating air. Grease a baking dish.
While the pasta is cooking, wash the spring onions and cut into thin rings. Finely dice or grate the mountain cheese, finely dice the mozzarella. Halve the cherry tomatoes. Mix the milk and eggs together. Season to taste with salt and pepper.
Drain and rinse the pasta. Pour into the baking dish and mix with spring onions, mountain cheese and some of the tomatoes. Pour the egg milk over it. Spread the remaining tomatoes and the mozzarella on the casserole.
Bake in the oven for about 35 minutes. Check whether the egg milk is curdled. If not, leave the casserole in the switched off oven for another 5 minutes.