In a medium bowl, combine grated carrots and brown sugar. *Set aside for 60 minutes, then stir in raisins.
Preheat oven to 350 degrees F and prep a muffin pan with cupcake liners.
In a large bowl, beat eggs until light. Gradually beat in the sugar, oil and vanilla. Stir in the crushed pineapple. In a separate mixing bowl, combine the flour, baking soda, salt and cinnamon and then stir into the wet egg mixture until combined. Finally stir in the carrot mixture and the walnuts. Pour evenly into the cupcake liners.
Bake for 25 to 30 minutes, or until a tester inserted comes out clean. Cool for at least 15 to 20 minutes before frosting.
For the frosting:
Using a stand mixer: mix together the butter and cream cheese until smooth, add the powdered sugar and vanilla and blend well. Spread on cooled cupcakes and enjoy!