DECORATING COOKIES
We’ve always liked the idea of decorations that provide a clue to a cookie’s flavor: a sprinkling of cinnamon and sugar to advertise a hint of spices; a few coconut shreds to signal a coconut filling. Coarsely chopped nuts or chocolate chips are wonderful toppings for big, flavorful, rough-textured cookies, but would be out of place on delicate wafers and crisps. Likewise, fine piping, tiny nonpareils, crystal sugar, or dainty dabs of jam are fine for tea cookies, but would seem fussy on hefty drop cookies and bars.
    To ensure that nonpareils and other garnishes will stay on top of cookies, press them firmly into the dough before baking (use a wide-bladed spatula if the cookies are flat)—or secure them after baking with Royal Icing. Cookies can also be decorated with food-coloring paint. To paint cookies before baking, whisk together an egg yolk, about 1/4 teaspoon water, and a drop of the desired food coloring. (Remember that blue coloring will turn green when mixed with the yellow yolk; for a true blue, use egg white instead.) For paint to be applied after baking, simply combine a drop of food coloring with a bit of water to dilute it to the appropriate intensity. (This color wash only shows up well on Springerle, sugar cookies, and other light-colored cookies.) Apply the paint in either case with a soft, fine-tipped paintbrush—or a small pastry brush if detail isn’t important.
    Don’t overdo it, though. A good general rule is to keep cookie decorations simple.