Preheat oven to 350 degrees F. Line a muffin tin with paper liners and set aside.
In a large bowl, cream the softened butter, white sugar, and brown sugar until light and fluffy.
Add in the eggs, one at a time, beating after each addition. Add in the pumpkin, 1/4 cup buttermilk, and vanilla extract
In another bowl, combine the flour, pumpkin pie spice, cinnamon, ginger, baking powder, baking soda, and salt. Mix. Add the dry ingredients to the wet ingredients in three parts, alternating each addition with 1/4 cup buttermilk (to use up the remaining 3/4 cup buttermilk).
Fill the prepared muffin tin liners 3/4 full (this batter makes exactly enough for 24 cupcakes). Bake 20-25 minutes, in the center of the oven, or until a toothpick inserted in the center comes out clean or with just a few moist crumbs.
Cool 10 minutes before removing from pans to wire racks to cool completely.
For the frosting: In a large bowl, beat cream cheese and butter until fluffy. Add powdered sugar, vanilla and cinnamon; beat until completely smooth.
Frost the cooled cupcakes. Best within 2-3 days.