Whisk together flour, baking powder, baking soda, salt, and Pie Spice in a medium bowl. In a separate bowl, whisk together egg and milk. In an electric mixer, beat butter and brown sugar until light and fluffy. Add egg mixture and beat until well combined. Add flour mixture and coconut and mix on low speed until just incorporated. Turn dough out onto lightly floured surface and shape into a 15-inch log. Flatten top and sides to form a rectangular log about 1 inch high and 3 inches wide. Wrap tightly in plastic wrap and refrigerate until firm, about 45 min. Preheat oven to 350 degrees. Cut chilled dough into slices about 1/4 inch thick and place on parchment-lined baking sheets about 1 inch apart. Dip the tines of a fork in flour and make crosswise indentations in dough slices. Sprinkle each cookie with Spiced Vanilla Bean Sugar. Bake until cookies are browned, about 15 min. It helps to rotate baking sheets halfway through baking time. Cool cookies on sheets for 10 min., then transfer to racks to cool completely.