Preheat oven to 350 degrees F and lightly grease and flour 3 (8x5) loaf pans and set aside.
Combine the butter, brown sugar and white sugar in a large bowl and beat until combined. Beat in the pumpkin puree, evaporated milk, eggs and vanilla until combined.
In a separate bowl whisk together the flour, baking soda, salt and pumpkin pie spice. Gradually add the dry ingredients into the wet and mix just until combined. Pour into the prepared pans until they're filled approximately 2/3rds of the way full. Bake for 45 to 50 minutes, or until a toothpick inserted in the center comes out clean. Let cool completely.
For the Icing:
Whisk together the icing ingredients until smooth. Spread over the cooled bread. Slice and enjoy!