Line a jelly roll pan with waxed paper. Melt semisweet chocolate in a double boiler. Stir in 3/8 teaspoon peppermint extract. Spread semisweet chocolate over the waxed paper. Spread the chocolate out to about 1/4 to 3/8 inch thickness.
Place pan in the refrigerator and allow chocolate to set for about 30 minutes. The chocolate does not need to be completely firm. Melt white chocolate in a double boiler and stir in 1/4 teaspoon peppermint extract. Spread white chocolate over the semisweet chocolate.
Sprinkle over crushed peppermint candies. Gently press candies into the chocolate. You want to press the candies into the chocolate. This will keep the peppermint candies from being easily knocked off when stored. Allow the chocolate to set up fully, this can take up to a couple of hours.
Once the chocolate has set break into pieces and store in an air tight container. This can be enjoyed for about two weeks after preparation. They key is not allowing the humidity to make the peppermints soggy.