Combine elk and 2 cups onion in a Dutch oven; cook over medium-high heat until lightly browned, stirring to crumble. Add wine; bring to a boil. Cook 3 minutes. Stir in 1 1/2 cups water, chile powder, and next 6 ingredients (through beans); bring to a boil. Partially cover, reduce heat, and simmer 2 hours (add more water if mixture becomes too thick). Ladle about 1 cup chili into each of 6 bowls; spoon 2 teaspoons sour cream over each. Sprinkle each with 2 teaspoons cheese and 1 teaspoon green onions.