Sauté each vegetable separately in 2 T. of butter. Set aside. Mix corn- starch with shredded cheese. Heat water to boiling in a large pot. Add cheese to boiling water gradually, stirring constantly. Add salt, pepper, Worcestershire, and garlic powder. Stir thoroughly.
Warm yogurt by stir- ring in some of the cheese mixture, then add yogurt to the soup. Add sautéed vegetables and heat through slowly.
