Preheat oven to 350 ° F. Line two baking sheets with parchment paper and coat with cooking spray. Set aside.
In a medium bowl, combine the brown sugar blend, applesauce, oil, egg substitute, and vanilla. Mix well and set aside.
In a large bowl, combine the flour oats, baking powder, baking soda, cinnamon, and nutmeg.
Make a weil in the center of the dry ingredients. Add the sugar (wet) mixture to the dry ingredients all at once and mix well.
Stir in the carrots. Scoop mounds of batter the size of a heaping tablespoon onto the baking sheets. Space them about 2 inches apart for a total of 24 cookies (2 sheets of 12).
Bake 15 minutes. Set aside to cool.
In a small bowl, beat the filling ingredients until smooth and fluffy. Spread a light layer of frosting between two cookies.