1. Preheat the oven to 350 F and line a 12 count muffin tin with cupcake liners.
2. In a medium-sized mixing bowl, combine together the flour, baking powder, baking soda, salt, cinnamon and nutmeg, and set aside.
3. In a large mixing bowl, whisk the brown sugar with the eggs until combined. Whisk in the oil, sour cream, and vanilla extract. Pour the dry ingredients into the wet, and use a large wooden spoon to gently combine; do not overmix! Gently fold in the carrots and pecans (if using).
4. Fill the cupcake liners about 3/4 full. Bake the cupcakes for 19-20 minutes, or until a toothpick inserted in the center comes out clean. Cool the cupcakes completely on a wire rack before icing.
5. Make the icing. In the bowl of a stand mixer fitted with the paddle attachment, or using a handheld electric mixer, beat the cream cheese with the butter on medium-high until light and fluffy, about 2 minutes. Add the vanilla, and one cup of the powdered sugar and mix on medium. Add the remaining powdered sugar, one cup at a time until you achieve your desired consistency. If you went overboard with the sugar, you can add a bit of heavy cream to thin out the icing. Decorate the cupcakes, and store any remaining icing in the fridge for up to 5 days.

Cupcakes can be kept at room temperature for 1-2 days, in an airtight container. I keep mine in the fridge! Cupcakes can also be frozen before icing, for up to 2 months.