Preheat oven to 350 degrees F. Line a baking sheet with parchment paper.

Place roasted chestnuts in a food processor, and grind until crumbly and fine.

In a large bowl, combine ground chestnuts, coconut flour, coconut sugar, and baking soda.

In a separate bowl, whisk together coconut oil, egg, and vanilla extract. Pour this mixture into the dry ingredients and mix well.

Fold in chopped chocolate.

Scoop with a large rounded tablespoon to drop dough onto the lined baking sheet. Flatten slightly.

Bake for 10-12 minutes, until slightly golden brown.

Cool completely before serving.