Oatmeal Ginger-Cream Pies

Preheat oven to 350 degrees F, with racks set in the top and bottom positions. On a baking sheet, bake oats on the top rack, shaking the pan intermittently to prevent burning, until lightly browned, 10 minutes. Transfer pan to a wire rack to cool, leaving oven on. Meanwhile, in a medium bowl, whisk together flour, baking powder, baking soda, cinnamon, nutmeg, ginger, and salt. In a large bowl, using an electric mixer on medium speed, beat butter and sugars until light and fluffy. Beat in the egg. Add the flour mixture, beating until just combined. Stir in the toasted oats. Fit 2 baking sheets with parchment. Roll dough, 2 tablespoons at a time, into balls, or use a #30 (1-ounce) ice-cream scoop; for each sheet, drop 12 balls 2 inches apart. With dampened hands, flatten each ball to a 1/2-inch thickness. Using the bottom and top racks, bake until cookies are lightly browned around the edges and set, 12 minutes, switching the baking sheets from top to bottom and rotating them from front to back halfway through baking. Remove from oven and let cookies cool for 5 minutes on baking sheets, then transfer cookies to a wire rack to cool completely. Frost the bottoms of 12 cookies with Ginger Cream, then top with the remaining 12 cookies.