Coat a 9-inch square pan with non-stick spray.

In a large saucepan, combine the butter, powdered sugar, and milk.

Cook and stir over medium heat until well-combined.

Bring to a boil and boil for 6 minutes without stirring.

Reduce heat to low, and add in white chocolate chips, stirring until they're mostly melted.

Remove from heat, and mix in peppermint extract.

Carefully transfer mixture to a large mixing bowl.

On low speed, gradually increasing mixer speed to medium, mix for about 1 minute, or until mixture is completely smooth.

Gently fold in peppermint baking chips and pretzels.

Garnish with sprinkles and a few additional pretzels, if desired, lightly pressing them into the fudge.

Refrigerate until set.

Cut into squares. Store in refrigerator.