Use an oven broiler 6 inches from the steak or a large, hot pan to cook the flank steak until rare, about 5 minutes on each side.
Once browned, remove beef from the heat source and it in to thin strips at a 45 degree angle. Set aside and keep warm.
In a large skillet, bring broth to a boil. Add onion and mushrooms; cover and simmer until tender, about 5 minutes.
In a small bowl, mix cold water, flour, and cornstarch until smooth. Whisk into the broth; cook and stir over low heat until thickened and bubbly. Remove from heat.
In a bowl, combine yogurt, paprika, and garlic powder; add to broth and stir until smooth. Add the beef; cook over low heat, stirring constantly, until thoroughly heated, about 5 minutes.
Serve over pasta or rice, opt for brown rice or wheat noodles for a nutritious boost.
