1. Beat the softened butter and powdered sugar together until smooth, creamy, and slightly fluffy.

2. Mix in the vanilla extract until fully combined.

3. In a separate bowl, whisk together the flour, cocoa powder, cinnamon, cayenne pepper, and salt.

4. Add the dry ingredients to the butter mixture and mix on low just until a soft dough forms.

5. Shape the dough into a firm, even log on parchment paper or plastic wrap.

6. Mix the optional granulated sugar and cinnamon, then roll the dough log in it if desired.

7. Wrap the dough tightly and chill for at least 1 hour, or until firm enough to slice.

8. Preheat the oven to 325°F and line baking sheets with parchment paper.

9. Slice the chilled dough into 1/4-inch rounds and place them on the prepared baking sheets.

10. Bake for 12 to 15 minutes, until the edges are set and the centers look dry.

11. Let the cookies cool on the baking sheet for 5 minutes, then move them to a wire rack.

12. Dip cooled cookies in melted chocolate if desired, then let the chocolate set before serving.