Recipe adapted from Oregon State University Extension's FoodHero.org.
In a large skillet, heat the margarine over medium-high heat (350°F in an electric skillet).
Add onion and mushrooms. Sauté and stir until they start to brown.
Meanwhile, in a small bowl, mix water, bouillon, garlic powder, and cornstarch. Add to skillet and cook until sauce is thickened.
Remove from heat. Stir in sour cream.
Serve with cooked whole grain noodles or brown rice. Garnish with paprika and chopped parsley, if desired.
Refrigerate leftovers within 2 hours.