For the Chocolate Pumpkin Cupcakes

1. Preheat the oven to 350°F and line a standard cupcake pan with 12 cupcake liners.
2. In a large bowl, cream together the butter and sugar until light and fluffy.
3. Add the egg, egg yolk, and vanilla extract, mixing until smooth.
4. Mix in the milk, sour cream, and pumpkin puree until well combined.
5. In a separate bowl, whisk together the sifted flour, cocoa powder, pumpkin pie spice, baking powder, baking soda, and salt.
6. Gradually add the dry ingredients to the wet ingredients, mixing until smooth.
7. Divide the batter evenly among the cupcake liners and bake for 17-19 minutes.
8. Let the cupcakes cool in the pan for 5 minutes before transferring them to a cooling rack to cool completely.

For the Pumpkin Cream Cheese Frosting

1. Measure out ½ cup of pumpkin puree and spread it onto a plate. Use paper towels to dab the pumpkin to remove excess liquid until it measures out to ¼ cup.
2. In a medium-sized bowl, beat the softened butter until pale and fluffy.
3. Add the cold cream cheese and mix until combined.
4. Mix in the dried pumpkin and pumpkin pie spice.
5. Gradually add the powdered sugar, mixing until light and fluffy.

Assembling the Cupcakes

1. Transfer the frosting to a piping bag fitted with a decorative tip.
2. Once the cupcakes are completely cooled, pipe a generous amount of frosting onto each one.
3. Serve and enjoy! Store any leftovers in an airtight container in the fridge for up to three days.