Preheat oven to 350° F. Line two sheet pans with parchment paper.

In a stand mixer with a beater attachment, cream together the melted butter and sugars until well combined.

Add the egg and yolk, one at a time, mixing after each addition. Add vanilla and mix to combine.

Scrape down the sides and bottom of the bowl.

In a medium-sized bowl, whisk together the flour, baking soda, cocoa powder, and salt.

Set mixer to low. Slowly add in the dry ingredients.

Once the last traces of flour disappear, mix in the chocolate chunks. Do not over-mix.

Remove bowl from mixer and run a rubber spatula around the bottom to make sure everything has been incorporated.

Dole out about 18, 2-tablespoon dough balls (I like to use a cookie or ice cream scoop) onto the parchment-lined pans, leaving about 2 inches between each ball.

Chill the pre-portioned dough in the fridge for 20 minutes. (This is crucial because it firms them up so they don't spread as much.)

Bake for 7 minutes, then swap and rotate the trays to promote even baking, giving each tray a solid *thwap* on the counter before returning to the oven.

Bake for 7 more minutes, then remove from the oven. After five minutes, transfer the cookies to a cooling rack.

While the cookies are cooling, make the buttercream.

In a stand mixer fitted with the paddle attachment, beat the butter on medium speed until light in color and fluffy.

Add the powdered sugar and mix until combined.

Scrape the bowl, then add in vanilla, peppermint extract, and a pinch of salt.

Beat the mixture just until it has all come together.

Add just the tiniest drop of red gel food coloring and beat to make a light pink color. Remember, you can always add more color, but you can never take it away!

Scrape down the sides of the bowl, then turn the mixer to low and let it run for about 3 minutes. This will help rid the buttercream of air bubbles.

Frost the cookies with the buttercream and sprinkle with crushed candy canes or peppermints.