Cream 1 cup of unsalted butter and 1 cup of confectioners' sugar together on medium speed until just combined, about 30 seconds. Incorporate 1 teaspoon of vanilla extract, 1/4 teaspoon of salt, and 1 teaspoon of peppermint oil until fully combined.

Gradually add in 2 cups of all-purpose flour and 1/2 cup of triple cocoa blend, mixing on low speed until a uniform dough forms, approximately 30 seconds.

Fold in 1 cup of chopped bittersweet chocolate, 1/2 cup of white chocolate, and 1/2 cup of crushed hard peppermint candies until evenly distributed.

Transfer the dough onto parchment paper and shape it into a log about 1.5 inches wide and 11 inches long. Wrap the log tightly in parchment and refrigerate for at least 2 hours.

Preheat your oven to 350°F (175°C). Remove the dough from the refrigerator and unwrap. Slice the dough into 1/2-inch thick rounds and place on baking sheets lined with parchment paper.

Bake for 12-14 minutes, rotating halfway through. Look for the cookies to puff slightly and the centers to appear set.

Cool on the baking sheets for about 10 minutes before transferring them to a wire rack to cool completely.