Twelfth-Night Pastry

The ritual of the thing—and the accompanying wine—may be more amusing than the pastry itself. The gâteau des Rois in the Parisian region—and, generally, in northern France—is a simple galette of puff pastry, the surface crisscrossed with a knife tip and painted with egg before being baked; sometimes it is a confection, less fanciful in form but resembling in composition a Pithiviers, of sweet, buttered, and lightly egg-bound almond paste, spread between plate-sized roun