Clean and quarter the mushrooms. Depending on how big they are. If you have little ones, then cut in half. Halve the onion and cut into thin slices. Press the garlic clove.
Now heat a pan with the fat and add the mushrooms. After about 3 minutes fry the onion and garlic. Fry everything well according to feel and heat.
Now the cream is added. Mix everything well. Let simmer for 2 minutes. Then mix in the parmesan. Stir well, otherwise the cheese will stick. Finally, season everything with salt and pepper.
Warm a fresh baguette in the oven and serve with the sauce. You can also serve this dish with pasta.