Meanwhile, Make the Cookies
Line 2 baking sheets with parchment paper. In a medium bowl, whisk the flour with the cornstarch, ground ginger, baking powder, salt and cinnamon. In a large bowl, using an electric mixer, beat the softened butter with the brown sugar at medium speed until fluffy. Beat in the egg yolks and molasses. Add the dry ingredients and beat at low speed until they are incorporated. Using a 2-tablespoon-size scoop, scoop 24 mounds of the dough onto the baking sheets and refrigerate until the dough is slightly firm, about 30 minutes.