Cut the onion into fine cubes. Clean the mushrooms and cut into strips.
Sweat the onion in the margarine in a pan, add the mushrooms and sauté briefly. Deglaze with white wine. Add the vegetable stock powder and soy cream and simmer over low heat, it is then not necessary to thicken.
Meanwhile, cook the spaghetti in salted water according to the instructions on the packet.
Season the sauce with a little salt, a little pepper, Provence herbs, vegetable stock powder and white wine.