Dice the onions, garlic and mushrooms. Put butter in a pan, sauté the onions, garlic and mushrooms until the mushrooms are smaller and the onion is translucent.
Prepare (cook) the spaetzle according to the instructions on the packet.
In the meantime, lightly grind the Gouda and blue cheese. When the onion is translucent, add the cheese and cream. Melt the cheese completely in the cream. Season to taste with parsley, vegetable stock, salt and pepper. If necessary, add 1 tablespoon sour cream (makes it a little lighter in taste).