Line a 11x17x1-inch jelly roll pan with parchment paper, allowing an overhang on all sides of the pan. Rub a bit of vegetable shortening or butter in the bottom of the pan corners as well as the sides of the pan to help the parchment paper stay in place.
Place the candy canes in a large Ziplock plastic bag. Use a rolling pin to crush the candy canes into pieces, about 1/4-inch. Separate the larger pieces from the powdery crumbs by shaking the candy through a sieve. Set the larger pieces and the powdery crumbs aside until ready to use.
Semisweet Chocolate Layer:
In the top of a double boiler over hot water, melt the semisweet chocolate. Remove from heat just before all the chocolate is melted. Stir with a clean and dry rubber spatula to finish melting the remaining chocolate. Learn How To Melt and Temper Chocolate.
When the chocolate has melted, add 4 drops of peppermint oil; stir until thoroughly combined.
Pour the melted chocolate onto the prepared baking pan and evenly spread over the bottom of the pan.
Place the pan in the refrigerator and chill until the chocolate is firm, approximately 20 to 30 minutes.
Remove the pan from the refrigerator while melting the white chocolate.This will allow the chilled chocolate to warm a bit to help the layer adhere.
White Chocolate Layer:
In a clean bowl, melt the white chocolate in the top of a double boiler over hot water. Remove from heat just before all the chocolate is melted. Stir with a clean and dry rubber spatula to finish melting the remaining white chocolate.
When the white chocolate is melted, add 4 drops of peppermint oil; stir until thoroughly combined. Stir in the candy cane powdery crumbs.
Pour the melted white chocolate directly over the top of the semisweet chocolate layer. Use a spatula to quickly spread the white chocolate evenly. Work quickly so that the semisweet chocolate does not start melting and blending into the white chocolate. Do not worry if the chocolates do start blending together, the candy will still taste delicious.
While the white chocolate layer is still soft, sprinkle the larger candy candy pieces as evenly as possible over the top. Use the back of a large spoon or a spatula to lightly press the candies into the chocolate.
Place the finished pan of Peppermint Bark in the refrigerator and chill the chocolates until firm, approximately 20 to 30 minutes. You could also leave the pan on the counter and let set until firm.
When the chocolates are firm, remove from the pan by grabbing the edge of the parchment paper and lifting out of the pan. Break the candy into irregular pieces or use a sharp knife or dough scraper to cut into rectangular pieces approximately 2- x 4-inches.
Store in an airtight container up to 2 weeks at room temperature.
Yields 2 pounds candy.