Prepare either silicon molds (place them onto a rimmed baking sheet so they are easy to move after filling) or a parchment lined 8x8-inch baking dish.

Combine the semisweet chocolate and 1 tablespoon coconut oil in a small microwave-safe bowl. Melt together over a double boiler (or in the microwave at 50% power, stirring every 30 seconds after about 2-6 minutes, heating until melted). Stir in 1/2 teaspoon peppermint extract (you can add more to taste if you like). Pour half of this mixture into the molds or parchment lined baking dish. Transfer to the freezer and let sit 5 minutes to solidify - you want the chocolate to look matte but it should not be fully set before you pour the next layer or it can break apart when slicing.

While the first layer begins to chill, prepare the white chocolate layer. Combine the white chocolate and 1/2 tablespoon coconut oil in a small microwave-safe bowl. Melt together over a double boiler (or in the microwave at 50% power, stirring every 30 seconds after about 2-6 minutes, heating until melted). Stir in 1/4 teaspoon peppermint extract, or more to taste. Pour all of this mixture into the molds or parchment lined baking dish. Transfer to the freezer and let sit 5 minutes to solidify - you want the chocolate to look matte but it should not be fully set before you pour the final layer.

Rewarm the semisweet chocolate, if it has begun to set, microwaving at 50% power or over a double boiler again. Pour over the white chocolate layer and again, transfer to the freezer and allow to set completely. Turn out of molds, if using, or slice into rectangles if poured into one sheet.