Preheat oven to 350 degrees F.
Line a muffin tin with paper liners and spray nonstick cooking spray over the top of the pan and liners; set aside.
In a large bowl, combine pumpkin, sugar, brown sugar, eggs, vanilla and sweetened condensed milk.
Add flour, pumpkin pie spice, salt, baking powder and baking soda and mix until well combined.
Fill each muffin cup with 1/3 cup of the batter.
Bake for 20 minutes, remove from oven and let cool.
For the frosting, combine butter, powdered sugar, vanilla, milk and salt and beat until light and fluffy.
Add more powdered sugar as needed for thicker frosting or add more milk to thin frosting to desired consistency.
Pipe frosting onto cooled cupcakes and sprinkle on a little pumpkin pie spice for garnish.