I suggest using pumpkin butter instead of just pureed pumpkin as it's a more concentrated version of pureed pumpkin. The pumpkin butter better imparts the pumpkin flavor without adding much more liquid to the milkshake. You can use store bought pumpkin butter or make your own with this pumpkin butter recipe.
Keyword autumn, fall, milkshake, pumpkim spice milkshake, pumpkin spice