Heat a Dutch oven over medium-high heat. Coat pan with cooking spray.
Add onion, bell pepper, garlic, and turkey to pan; saut 8 minutes or until turkey is browned and vegetables are tender.
Add sugar and next 9 ingredients (through chipotle) to pan, stirring to blend; bring to a boil. Reduce heat; simmer 15 minutes or until slightly thickened, stirring occasionally.
Add chocolate, stirring to melt. Ladle 1 1/4 cups chili in each of 8 bowls; top each serving with 1 tablespoon sour cream.