Chocolate chunks: mix the cocoa, yolk, and sweetener well. Pour onto a piece of parchment paper and place in the freezer for ~2 hours. Cut into chunks.

Preheat oven 350 F after the chocolate chunks are ready. Line a baking sheet with parchment paper.

Dough: mix the rest of the ingredients together. Fold in the chocolate chunks.

Drop spoonfuls of dough on the parchment paper, for about 15-20 cookies. Bake ~20 minutes. Let cool, remove and freeze for storage.