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 light. Add the egg and vanilla, mixing until smooth and incorporated.
04 - Gradually stir in the dry ingredients until just combined. Be careful not to overmix.
05 - Fold in grated carrots, oats, and any optional add-ins including nuts and raisins until evenly distributed throughout the dough.
06 - Drop tablespoonfuls of dough onto the prepared baking sheet, spacing cookies 2 inches apart to allow for spreading.
07 - Bake for 10-12 minutes, or until edges are lightly golden and centers appear set. Allow cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.
08 - For the optional frosting, beat cream cheese and butter until smooth and creamy. Add powdered sugar and vanilla, mixing until fluffy and spreadable. Spread or pipe onto completely cooled cookies.