Step 1

For the cookies: Preheat the oven to Line 2 to 3 baking sheets with parchment paper.

Step 2

Beat the granulated sugar and butter on medium speed in the bowl of a stand mixer until light and fluffy, 2 to 3 minutes. Reduce the mixer speed to low. Mix in the egg, then the buttermilk, food coloring, and vanilla.

Step 3

Whisk the flour, cocoa powder, baking powder, and salt in a medium bowl. Mix the flour mixture into the butter mixture in two batches with the mixer on low speed. Scrape the bowl once and mix a final time until well combined. Fold in the white and semi-sweet chocolate chips.

Step 4

Scoop dough using a 2 tablespoon scoop, and place cookies about 2 inches apart on the prepared pans. Grease the bottom of a glass and press cookies to be about ½ inch thick. Sprinkle with 1 tablespoon sparkling sugar. Bake until the cookies are puffy and set on the edges but centers remain slightly soft, about 10 minutes. Sprinkle with the remaining 1 tablespoon of sparkling sugar. Let cool 2 minutes on the pans, then remove the cookies to a rack to cool completely.