Combine first 4 ingredients in a medium bowl, and stir well. Spread about 1/2 cup bean mixture over each of 4 tortillas, and top each with 3 tablespoons cheese and remaining tortillas.

Coat a large nonstick skillet with cooking spray, and place over medium-high heat until hot. Add 1 quesadilla, and cook 3 minutes on each side or until golden. Remove quesadilla from skillet; set aside, and keep warm. Repeat procedure with remaining quesadillas.

Cut each quesadilla into 4 wedges. Serve warm with sour cream. Garnish with cilantro sprigs and jalapeño peppers, if desired.