Saute garlic and onion in oil in a med.-size soup pan. Add sugar and chili powder. Add tomato puree and broth. Simmer 30 min. Mix 4 tbsp. Chili peppers with cornstarch in bowl. Add to soup. Simmer 2 min. Remove from heat. Put 1-1/2 cups sour cream into a bowl. Stir ladle of soup into it. Return sour cream mixture to pot. Place over low heat. Stir gently.

Taste, and season with salt, if desired. Serve cold. Fold a tbsp. Dollop of sour cream or yogurt onto each plate and sprinkle with green chilies, if desired.