In a large bowl sift together flour, baking powder, and salt. Set aside. Place butter and sugar in bowl of electric stand mixer and beat until light and fluffy, about 3 minutes. Add the egg and milk and beat to combine. Put mixer on low speed, gradually add flour, and beat until mixture pulls away from the side of the bowl. Divide the dough in half, cover with plastic wrap, and refrigerate at least 2 hours.
Preheat oven to 375 degrees F.
Remove 1 wrapped pack of dough from refrigerator at a time, un-wrap the dough and roll it by hand into a log about 1 1/2-inches in diameter. Repeat with the second pack of dough. If dough has warmed during rolling, return it to the refrigerator for about 10 minutes. The dough may even be frozen at this point and thawed when ready to bake.
Sprinkle a work surface with half of the turbinado sugar. Roll one of the logs through the pile coating the entire log with as much of the sugar as will adhere. Repeat with the remaining sugar and the second log. Slice each log crosswise into 1/3-inch thick rounds. Place them at least 1-inch apart on greased baking sheet, parchment, or silicone baking mat, and bake for 8 to 9 minutes or until cookies are just beginning to turn brown around the edges, rotating cookie sheet halfway through baking time. Let sit on baking sheet for 2 minutes after removal from oven and then move to complete cooling on wire rack. Store in airtight container for up to 1 week.