Cook the pasta in 2 liters of water with salt, granulated broth and olive oil for 7 minutes. Drain, collect the cooking water, measure out 400 ml and set aside.
Cut the meat sausage into fine strips, divide the cauliflower into tiny florets, mix with the penne and place in a baking dish.
For the sauce, dice the onion very finely. Sweat half of it, toast the other half. Boil the cooking water with the onions, the chives, the cream, the milk, the mustard, the herbs and the beaten egg for 1 minute.
Pour over the pasta in the baking dish. Place the cheese slices on top and bake in the preheated oven for 20-25 minutes at 200 ° C.