Chop the onion and fry in a pan. I missed this step, because my favorite pre-fried a lot of onions, and they are in the freezer and waiting in the wings. So I already have a ready-made bow.
Mushrooms cut into plates 3-4 mm thick and lightly fry in a frying pan (I have a wok) in vegetable oil. I had 1 kg of mushrooms here, but after roasting, I selected half as a preparation for the future.
Wash the mussels thoroughly in cold water, then pour in cold water, mix, let stand for about 10-15 minutes and select the mussels with your hands in another bowl. This is necessary so that the grains of sand and shell particles remain on the bottom.
Add the mussels to the mushrooms and continue cooking over medium heat. Then add the fried onions to them.
Dilute the homemade sour cream with water and pour it into the pan. Add the cream. In principle, you can only do with cream, but then you need to take 600 ml. I do not recommend using store-bought sour cream, as it may curdle.Add salt, spices (I have a mixture of peppers, 3 small Bay leaves, a mixture of dried herbs, dried garlic) and simmer for 10 minutes.