Trim and slice round steak into thin strips.
In a large skillet melt 2 Tbsp butter. Sauté chopped onions until soft then add the round steak,brown for about 5 minutes, remove and keep warm.
Add 1 Tbsp butter and sauté sliced mushrooms to skillet. Stir in tomato paste, 2 Tbsp water, and basil. Return the meat mixture to the skillet and simmer 5 minutes.
In a separate small saucepan, mix cornstarch with yogurt and cook over medium heat until thickened. Add to the meat mixture and heat through. Thin with 1/4 cup water, if needed. Serve over the cooked noodles.Servings: 4