Melt butter in a large stock pot over medium heat.
Add one and a half bags of the marshmallows (reserving half of a bag for later). Stir until melted.
Remove from heat and stir in peppermint extract.
Add rice krispies and stir until evenly coated.
Add remaining marshmallows and white chocolate chips. Stir until evenly combined.
Line a 9x13" baking dish with parchment paper. Spray lightly with nonstick spray.
Pour rice krispies into the baking dish and press down firmly with wet hands.
Sprinkle with crushed peppermint candy. Press down firmly.
Let chill until set. Cut into squares.