Set up your double boiler and bring water to a gentle simmer.

Combine chocolate chips, butter, and sweetened condensed milk in the double boiler. Stir until smooth and glossy, about 5 to 7 minutes.

In a separate bowl, melt white chocolate chips and sweetened condensed milk until smooth.

Add peppermint extract and red gel food coloring to the white chocolate mixture; mix gently.

Pour ¾ of the chocolate mixture into a greased pan, then drop spoonfuls of the peppermint mixture over it.

Use a skewer or knife to create swirls in the layer.

Pour remaining chocolate mixture over the swirls, spreading to cover.

Sprinkle crushed peppermint candy on top, pressing down lightly.

Refrigerate uncovered for at least 3 hours until set.

Use a hot knife to cut into squares for serving.