Add butter, chocolate chips, sweetened condensed milk, and vanilla extract to a bowl placed over a double boiler. Stir with a spatula until melted and smooth.
Line a baking sheet with parchment paper and place your cookie cutters on top. Spray the inside of the cookie cutters with a non-stick spray.
Fill the cookie cutters with the fudge, making sure to reach all the corners and small sections.
Press peppermint chips onto the fudge
Move baking sheet to the fridge to chill - 2 hours or until firm
Press the fudge from the cookie cutter and set aside