In a small bowl, whisk together the all-purpose flour, baking soda, and kosher salt until well combined. Set this bowl aside while you prepare the wet ingredients.

In a large mixing bowl, use an electric mixer to beat the softened unsalted butter, granulated sugar, and brown sugar together for about 3-4 minutes until light and fluffy.

Add the large egg and pure vanilla extract to the butter and sugar mixture, mixing on medium speed until blended.

Gradually incorporate the dry mixture into the wet mixture, mixing until just combined.

Fold in the peppermint crunch baking chips and bittersweet chocolate chips with a spatula, ensuring they are evenly distributed.

Cover the cookie dough tightly with plastic wrap and refrigerate for at least 2 hours, or ideally overnight.

Preheat your oven to 350°F (175°C) and line your baking sheets with parchment paper.

Using a 3-tablespoon cookie scoop, portion out the chilled dough onto the prepared baking sheets, leaving about 2 inches of space between each mound.

Bake for about 15-18 minutes or until the edges are golden brown while the centers remain soft and gooey.

Allow the cookies to cool on the baking sheet for about 5 minutes before transferring them to a wire rack.