Preheat oven to 400Â°. Spray 8- or 9-inch square pan with cooking spray.
In small bowl, stir together Bisquick, water and egg; spread in pan. Sprinkle with 1-1/4 cups of the cheese.
In a 10-inch nonstick skillet, cook chicken over medium-high heat, stirring frequently, until outsides turn white; drain. Stir in salsa; heat until hot. Spoon over batter in pan to within 1/2 inch of edges.
Bake 22 to 25 minutes or until edges are dark golden brown. Sprinkle with remaining 1/4 cup cheese. Bake 1 to 3 minutes longer or until cheese is melted; loosen from sides of pan.