Preheat oven to 425ºF. Line a baking sheet with parchment paper and set aside.
In a large bowl, add flour, brown sugar, cocoa powder, baking powder, baking soda, and salt. Whisk to combine.
1 ⅜ cups all-purpose flour, 5 Tablespoons brown sugar, ¼ cup unsweetened cocoa powder, 2 teaspoons baking powder, ½ teaspoon baking soda, ¼ teaspoon salt
Add cold butter cubes to bowl. Cut the butter into the flour mixture using a pastry blender until a crumbly dough forms.
6 Tablespoon unsalted butter,
Combine buttermilk and vanilla and add to the dough. Toss gently using a fork just until all of the dough is moistened and there's no dry flour. Do not stir or over mix the dough.
⅝ cup buttermilk,, 1 teaspoon vanilla extract
Transfer the dough onto a lightly floured surface. If necessary, use your hands to gently bring the dough together. Roll out the dough into a circle that's 1 inch thick.
Use a 2.5 inch round cutter to cut 6 biscuits from the dough (you will need to re-roll dough scraps to get 6 biscuits).
Place the dough circles 1 inch apart on the prepared baking sheet. Bake for 13-15 minutes, or until a toothpick inserted into the side of a biscuit comes out clean. Let biscuits cool on a wire rack or serve warm.
Video
Notes
Storage: Biscuits are best when freshly baked but will keep in an airtight container at room temperature for up to 2 days.