In a medium saucepan, over low heat, combine sweetened condensed milk, white chocolate chips, and semi-sweet chocolate chips. Stir continuously for about 5-7 minutes until melted and smooth.

Remove from heat and stir in the peppermint extract until fully incorporated. Allow the mixture to cool slightly.

Divide the fudge mixture into two bowls. Add red food coloring to one half and swirl gently in a lined baking pan to create a marbled effect.

Sprinkle crushed peppermint candies on top and press lightly to adhere.

Chill in the refrigerator for at least 2 hours, then cut into squares.