Heat a large pot under medium heat and add butter until melted.
Lower heat to low/ medium low. Add marshmallows, vanilla, and peppermint extract. Stir continuously until mixture is combined and marshmallows have dissolved.
Remove from heat. Fold in Rice Krispie cereal.
Grease a 8 x 8 pan and fill with sticky Rice Krispie mixture. Spread to fill the pan without packing in the cereal. It would be more difficult to cut if it is packed in.
In separate bowls, melt milk chocolate and white chocolate by mixing the each of the chips with 1/2 tsp vegetable oil. Melt in microwave set at 50% power for 30 second increments. Stir after each 30 seconds. Continue until chocolate and white chocolate are melted.
Drizzle the melted milk chocolate and white chocolate on top of the Rice Krispies.
Sprinkle with crushed peppermint candies.
Let sit and cool for 30 minutes. Cut into squares.
Serve and enjoy!