I think this is a great recipe from the Simply Simpatico cookbook put out by the Junior League of Albuquerque, New Mexico. This also makes an excellent appetizer. Cooking time does not include the 1 hour refrigeration time.
Combine beef, egg, corn chips, milk and 1 teaspoon salt in large bowl. Cover and chill 1 hour.
Shape into 15 meatballs, using 2 tablespoons meat mixture for each.
Place flour in small shallow bowl or plate and roll meatballs in it lightly, coating completely.
In large, heavy skillet, melt butter. In batches, saute meatballs in butter until nicely browned all over. When browned, remove meatballs.
In the same skillet, saute onion and garlic, stirring occasionaly, about 5 minutes. Remove from heat.
In a small bowl, combine sugar, chili powder, cumin, coriander, oregano, and remaining salt and flour.Stir into skillet along with tomatoes, chocolate, and 1 cup water, mixing well. Bring to boil, stirring constantly. Reduce heat; cover pan and simmer 30 minutes, stirring occasionally.
Add meatballs to skillet; cover and simmer 20 more minutes.