01 - Preheat oven to 350°F. Line a baking sheet with parchment paper.
02 - In a medium bowl, whisk together flour, baking powder, baking soda, salt, cinnamon, ginger, and nutmeg until well blended.
03 - In a large bowl, beat butter, brown sugar, and granulated sugar together until creamy and lightened in color, about 2 minutes.
04 - Add the egg and vanilla extract to the butter mixture, beating until fully incorporated and smooth.
05 - Gradually stir the dry ingredients into the wet mixture, mixing just until combined. Do not overmix.
06 - Gently fold in grated carrots, oats, and any optional add-ins including nuts and raisins until evenly distributed.
07 - Drop tablespoonfuls of dough onto the prepared baking sheet, spacing cookies 2 inches apart to allow for spreading.
08 - Bake for 10-12 minutes, or until edges are lightly golden and centers are set. Allow cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack.
09 - Beat softened cream cheese and butter until smooth and creamy. Add powdered sugar and vanilla extract, mixing until fluffy and well combined.
10 - Once cookies are completely cooled, spread or pipe the frosting onto the tops of the cookies. Serve immediately or store in an airtight container.