1. Melt butter in a large Dutch oven over medium-high heat. Add onions, bell pepper, and serrano chile to pan; sauté 2 minutes or until tender, stirring frequently. Add canned chiles to pan; cook 1 minute. Add flour to pan; cook 1 minute, stirring constantly. Stir in milk and next 5 ingredients (through corn); bring to a boil. Cook 5 minutes or until slightly thick. Stir in shrimp; cook 1 minute or until shrimp are done. Remove from heat; stir in cilantro.
Quesadillas: Heat a large nonstick skillet over medium-high heat. Coat pan with cooking spray. Place 2 (6-inch) flour tortillas in pan. Top each tortilla with 2 1/2 tablespoons preshredded reduced-fat Mexican blend cheese, 1 1/2 tablespoons chopped green onions, and 1 tablespoon chopped pickled jalapeño peppers. Cook 1 minute or just until cheese melts and tortilla is toasted. Arrange 1 (6-inch) flour tortilla over top of each quesadilla. Flip quesadillas; cook 30 seconds. Cut each quesadilla into 6 wedges, and serve with a small bowl of salsa.