Preheat the oven to 300° F.

Combine the flour, sugars, cocoa powder, salt, and nutmeg in the bowl of a food processor and process for a few seconds to combine. Add the butter and the vanilla and process until the dough comes together into a ball.

Turn the dough out onto a sheet of wax or parchment paper and shape into a disk. Wrap in plastic and refrigerate for at least an hour, or until the dough is chilled and firm.

Remove from the refrigerator and roll the dough out on a lightly floured surface to a thickness of 1/4-inch. Cut out the cookies using a 3 1/2-inch heart shaped cutter. Transfer the cookies to a baking sheet lined with parchment paper.

Bake the cookies for 20 minutes, rotating the sheets halfway through baking. Cool the cookies completely on a wire baking rack.