Step 1: Preheat your oven to 350°F (175°C) and line two large baking sheets with parchment paper or silicone mats.
Step 2: In a large mixing bowl, cream together the softened butter, granulated sugar, and brown sugar until light and fluffy, about 2-3 minutes.
Step 3: Beat in the egg and vanilla extract until well combined and smooth.
Step 4: In a separate medium bowl, whisk together the flour, cocoa powder, cinnamon, cayenne pepper, baking soda, and salt.
Step 5: Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined. Fold in chocolate chips if using.
Step 6: Scoop rounded tablespoons of dough and roll them into balls. Place them 2 inches apart on the prepared baking sheets.
Step 7: Bake for 8-10 minutes, or until the edges are set but the centers still look slightly soft. Do not overbake.
Step 8: Sprinkle a tiny pinch of coarse sea salt over the warm cookies. Let them cool on the baking sheet for 5 minutes before transferring to a wire rack.