LINE 9-inch-square baking pan with parchment paper, leaving a one-inch overhang on 2 sides for easy removal from pan. Set aside.
COMBINE butter and marshmallows in a large saucepan; cook over medium heat, stirring occasionally, until smooth. Stir in cocoa powder, vanilla extract and pumpkin pie spice; remove from heat.
PLACE popcorn, Raisinets and pretzels into large bowl. Drizzle cocoa mixture over and toss until well coated.
PRESS into prepared pan. Cool for about 20 minutes or until set. Cut into 16 squares.