1. Preheat your oven to 350°F and line a baking sheet with parchment paper.
2. In a medium bowl, whisk together flour, cocoa powder, baking soda, and salt.
3. In a large bowl, cream together the butter and sugar until light and fluffy, about 3 minutes.
4. Add the egg and vanilla extract to the butter mixture, mixing until well combined.
5. Gradually fold in the dry ingredients until the dough comes together.
6. Scoop tablespoon-sized portions of dough onto the prepared baking sheet, spacing them about 2 inches apart. Flatten each slightly with the back of the spoon.
7. Bake for 8-10 minutes, until the edges are set. Let the cookies cool completely on a wire rack.
8. Once the cookies are cool, scoop a generous amount of ice cream onto the flat side of one cookie. Top with another cookie to form a sandwich.
9. Roll the edges of the ice cream sandwiches in the popping candy, pressing gently to adhere.
10. Wrap each sandwich in plastic wrap and freeze for at least 1 hour before serving.

From experience, make sure the ice cream is just soft enough to scoop but not too melty, or you’ll have a sticky mess on your hands—one of those lessons learned the hard way!