01 - In a medium bowl, whisk together flour, cocoa powder, cinnamon, baking powder, and salt until evenly blended.
02 - In a large bowl, beat butter and sugar with an electric mixer until light and fluffy, approximately 2 minutes. Add egg and vanilla, mixing until fully incorporated.
03 - Gradually add the dry ingredients to the wet mixture, mixing on low speed just until a dough forms. Avoid overmixing to prevent tough cookies.
04 - Divide dough in half and flatten into disks. Wrap tightly in plastic wrap and refrigerate for at least 30 minutes until firm enough to roll.
05 - Preheat oven to 350°F and line baking sheets with parchment paper.
06 - On a lightly floured surface, roll dough to 1/4 inch thickness. Cut out skeleton or gingerbread man shapes using cookie cutters.
07 - Place cookies 2 inches apart on prepared baking sheets. Bake for 10-12 minutes until edges are set. Cool completely on wire racks before decorating.
08 - In a clean bowl, beat egg white with powdered sugar and water until smooth and thick enough to pipe. Adjust consistency with additional water if needed.
09 - Transfer icing to a piping bag fitted with a fine round tip. Pipe skeleton designs onto cooled cookies and allow icing to dry completely before storing.