Line an 8-inch square baking pan with parchment paper, leaving enough overhang on two sides to lift out the chilled fudge.

Combine the white chocolate chips and sweetened condensed milk in a microwave-safe bowl. Microwave in 30- to 60-second intervals, stirring thoroughly after each interval, until smooth; alternatively, melt them in a saucepan over low heat while stirring constantly.

Remove the smooth mixture from the heat immediately. Stir in the peppermint extract, optional vanilla extract, and salt, then add optional food coloring if desired.

Fold about half of the crushed peppermint candies into the warm fudge mixture.

Spread the mixture evenly into the parchment-lined pan. Sprinkle the remaining crushed peppermint over the surface and gently press it into the fudge.

Refrigerate the pan for 2 to 3 hours, or until the fudge is firm. Lift it out using the parchment overhang and cut it into small squares with a sharp knife.