Place your oven racks in the lower and upper thirds of your oven and preheat to 350 degrees.
Spread the rolled oats out on a cookie sheet and bake on the upper oven rack for 10 minutes, shaking the pan once or twice half way through baking to prevent burning. Once toasted, remove from the oven and allow to cool.
Line 2 large cookie sheets with parchment paper and set aside.
In a mixing bowl, whisk together the flour, baking powder, baking soda, cinnamon, nutmeg, ginger and salt.
With a mixer, beat the butter, granulated sugar and brown sugar on medium speed until light and fluffy.
Beat in the egg and add the flour mixture, beating until just combined. Stir in the rolled oats.
Roll 2 tablespoons of the cookie dough into a ball and place onto the cookie sheets 2" apart. With a damp hand, flatten each ball until they're a 1/2 inch thick.
Bake for 12 minutes, switching the cookie sheets from the top rack to the bottom rack half way through, or until cookies are lightly browned around the edges and set.
Allow to cool on the cookie sheet for 5 minutes and then transfer to wire cooling racks to cool completely.
Using a mixer, beat the cream cheese and confectioner's sugar until smooth. Beat in the ginger just until combined.
Spread the cream mixture onto 12 cookies and then top with a second cookie.