Homemade mushroom soup

HOMEMADE MUSHROOM SOUP

8-12 oz fresh mushrooms
1 small onion, slice thin
¼ cup margarine
3½ cups milk
1/3 cup flour, mixed to a smooth paste with ¼ cup cold milk
4 chicken bouillon cubes
Pinch of thyme
½ cup plain yogurt

Brown the mushrooms and onions in margarine for about 5 minutes. Add milk, flour paste, chicken bouillon and thyme. Heat over moderate heat, stirring frequently, until soup is thick. Remove from heat. Season with salt and pepper. Stir a little bit of the hot soup into the yogurt. Stir all of yogurt mixture into the hot soup. Serves 4.