In a large skillet cook bacon over medium heat until bacon starts to crisp, stirring often. Add onion and garlic; cook and stir for 5 minutes or until onion is tender. Add mushrooms; cook and stir until tender. Remove from heat. Stir in crushed red pepper, Worcestershire, and cilantro.
In another large skillet or on a griddle melt 1 piece of the butter over medium heat. For quesadilla, sprinkle 1/4 cup cheese over half of each tortilla. Top cheese with 1/3 cup of the mushroom mixture. Fold tortillas, in half, pressing gently. In prepared skillet cook one quesadilla for 2 to 3 minutes or until lightly browned, turning once. Remove quesadilla from skillet; place on baking sheet. Keep warm in a 300 degree F oven. Repeat with remaining butter and quesadillas. Spoon sour cream into a bowl; sprinkle with tomato, sweet pepper, and green onion. Cut quesadillas into wedges; serve with sour cream sauce. Makes 4 appetizer servings.