1/4 cup milk
1 cup salted butter, softened to room temperature
1/3 cup canned pumpkin puree, mixed
1/2 cup powdered sugar
1 tbsp cinnamon
3/4 tsp nutmeg
1/2 tsp ground ginger
1/2 tsp allspice
1/2 vanilla bean, scraped
Measure milk and set out for 20 minutes at least before starting. In a bowl of a stand mixer or hand mixer and beat milk and butter on low to medium low until combined. This may take a long time.
Increase mixer speed to medium high and beat for 5 minutes, scraping down sides as it goes, until butter is light and fluffy. Add remaining ingredients and beat on low until incorporated, then turn on medium-high and beat for 1 additional minute.