Wash the broccoli and cut into florets, cut the stalks into small pieces and blanch them in salted water for 3 minutes, place in a greased baking dish and sprinkle with 100 g of grated cheese, gratinate at 180 degrees for 15 minutes. In the meantime, stir the sour cream with the vegetable stock and flour until smooth, bring to the boil in a saucepan while stirring and simmer for a few minutes, season with salt and pepper. Stir in the rest of the cheese and don`t let it boil anymore, refine with chopped parsley. Arrange the broccoli on 4 plates and nap with the sauce, sprinkle with parsley if necessary.