- If soaking mushrooms, cover with water and let sit for 30–40 minutes.
- Squeeze out excess water.
- Clean mushrooms and slice thinly.
- Melt margarine in a large pan and add onion, garlic and mushrooms.
- Cook over medium heat for 10 minutes.
- Add all other ingredients and mix well (use a whisk for the flour).
- Continue cooking until well mixed and completely cooked, about 10-15 more minutes.
- Serve over cooked fettucini.
- Sprinkle with scallions or parsley for garnish.