Preheat your oven to 350°F and prepare a cupcake pan with liners.

Whisk together flour, baking powder, baking soda, salt, and pumpkin pie spice in a medium bowl.

Cream the softened butter with brown sugar and granulated sugar until smooth, about 2 minutes.

Add eggs, vanilla extract, pumpkin puree, sour cream, and milk to the butter mixture. Blend well, scraping down the sides of the bowl.

Gradually mix the dry ingredients into the wet mixture on low speed, being careful not to overmix.

Spoon batter into cupcake liners, filling each halfway. Bake for 18–20 minutes, or until a toothpick inserted in the center comes out clean.

Let the cupcakes cool completely on a wire rack.

Beat butter and cream cheese together until smooth for the frosting.

Gradually mix powdered sugar into the cream mixture on low speed.

Add vanilla extract, cinnamon, and heavy cream, then whip on high speed for 3–5 minutes until the frosting is fluffy.

Generously frost the cooled cupcakes and serve.