Roast the buckwheat in a dry, wide lidded pan, stirring, for 5 min. until brown. At the same time, boil 3/4 l salted water in a saucepan, pour over buckwheat, cover and cook over low heat for 5 min. Remove from heat and let swell for 10 min. Peel and dice onions. Wash spring onions and cut white end and green separately into rings.
Carefully clean oyster mushrooms and mushrooms with kitchen paper or mushroom brush and cut into 1/2 cm thick slices. Wash and chop the parsley. Saute the red onions and the whites of the scallions in oil for 2 – 4 min. Saute the mushrooms over medium heat until all the liquid has evaporated.
Sprinkle the mushrooms with rosemary, thyme and scallion greens. Season with sea salt and pepper. Add the broth, bring to a boil and mix with the sour cream. Serve together with the buckwheat.
