Fill a large skillet halfway with water; bring to a boil. Poach chicken 7 min or until cooked through. Let cool, then shred with two forks.

Remove skillet from heat and wipe clean. Coat skillet generously with nonstick cooking spray and place over medium-high heat. Cook mushrooms 5 minutes, stirring occasionally, or until softened.

Spread all 4 tortillas with 1/4 cup refried beans. Divide cheese, chicken and mushrooms between 2 of the tortillas. Place remaining 2 tortillas on top, bean-side down.

Return skillet to medium-high heat. Coat skillet and tops of quesadillas with nonstick cooking spray. Cook one quesadilla 4 minutes per side or until cheese has melted, reducing heat to medium if tortilla becomes too brown. Repeat with remaining quesadilla. Cut both quesadillas in half and serve with salsa.