1 tsp. olive oil
20 white button mushrooms, sliced thin
1/2 yellow onion, sliced thin
1 cup mushroom or vegetable broth
1 Tbsp. potato starch dissolved in 2 Tbsp. cold broth
1/4 cup sour cream
Cook pasta according to package. Slice mushrooms & onions. Put oil in a large, heavy skillet, and sauté onions until they soften, 2-3 minutes. Add mushrooms and sauté another 3-4 minutes, until onions are very soft and mushrooms are cooked. Remove from pan and reserve. Turn heat to high and add broth. Let cook 5 minutes. Turn heat to low, add reserved vegetables and cook 1 minute. Push food to the sides of pan and stir potato starch/broth mixture into the middle in a thin stream. Stir pan and cook until sauce thickens slightly, about 1 minute. Turn off heat and add sour cream. Serve over baked potatoes.