In a large saucepan, melt the butter over low heat. Once melted, add the mini marshmallows and stir until completely melted and smooth.

Remove from heat and stir in the vanilla extract.

Gradually add the Rice Krispies cereal, mixing until well coated with the marshmallow mixture.

Grease a baking dish with cooking spray or butter. Press the mixture into the dish evenly, using a spatula or wax paper to help.

Allow the mixture to cool for about 30 minutes.

Once cooled, cut the mixture into ghost shapes using a cookie cutter or by hand.

Melt the white chocolate wafers according to package instructions. Dip the top of each ghost in the melted chocolate to coat.

Before the chocolate sets, place chocolate chips on the ghosts to create eyes.

Let the chocolate harden before serving.