Preheat oven to 350° F. Grease an 8-inch square baking dish and set aside.
In a large bowl, cream together brown sugar, butter and egg until light and fluffy. Add carrots and vanilla; mix well.
In a small bowl, whisk together flour, baking powder, cinnamon, nutmeg, ginger, allspice, cloves and salt.
Add dry ingredients to the butter mixture; mix just until combined.
Stir in oats and raisins.
Spread batter in prepared baking dish.
Bake for 30 minutes, or until the center is set. Cool completely on a wire rack.
Once the bars are cool, prepare the cream cheese glaze by stirring together cream cheese and confectioners’ sugar in a small bowl. Add milk, stirring to combine. Drizzle over the bars; slice and serve.