Prepare the Baking Dish: Line an 8x8 inch baking pan with parchment paper, leaving some overhang for easy removal later.
Melt Semi-Sweet Chocolate: In a medium saucepan over low heat, combine the semi-sweet chocolate chips, sweetened condensed milk, and salt. Stir constantly until fully melted and smooth.
Add Peppermint: Remove the saucepan from heat and stir in the peppermint extract, mixing well. If desired, add a few drops of red food coloring to create a marbled effect.
Add to Pan: Pour the melted chocolate mixture into the prepared baking dish. Spread it evenly with a spatula.
Prepare White Chocolate Layer: In the same saucepan, melt the white chocolate chips over low heat, stirring until smooth.
Combine with Peppermint: Once melted, remove from heat and stir in the remaining crushed peppermint candies.
Top the Fudge: Pour the white chocolate mixture over the semi-sweet chocolate layer in the baking dish. Use a spatula to spread it evenly on top.
Add Extra Peppermint: Sprinkle additional crushed peppermint candies on the top for decoration.
Chill: Place the baking dish in the refrigerator for at least 2 hours or until the fudge is firm.
Cut and Serve: Once set, remove the fudge from the pan using the parchment paper overhang and cut into squares.
Notes
Serve on a festive platter with edible glitter for a holiday touch.