Drain liquid from the puree then push through a strainer to remove any lumps and stringy bits. Place puree in a small saucepan with the brown sugar and spices. Cook over medium-low heat until the puree simmers and the sugar dissolves completely. Set aside.
Make an ice bath – place a few ice cubes and a few cups of water in a large bowl. Set aside. Have a clean bowl or container and a fine mesh strainer standing by.
Mix sugar, non-fat milk powder, and tapioca starch. In a separate bowl combine milk and cream. Whisk in the dry ingredients. Add corn syrup and continue whisking until there are no lumps.
Place the mixture in a medium saucepan over medium-high heat. Cook for 8-10 minutes. Do not let it come to a boil. Keep stirring the mixture while it cooks. In the last few minutes stir without stopping as the mixture begins to thicken.
Once it’s thick enough to coat the back of a wooden spoon, pour it through a fine mesh strainer into the bowl that is standing by. Using an immersion blender (or regular blender) thoroughly incorporate the pumpkin puree and whiskey.
Place a piece of plastic wrap on the surface of the gelato to prevent a skin from forming. Put the bowl of hot gelato into the ice bath.
After the gelato has cooled, remove from the ice bath and refrigerate for 4-12 hours.
Give the gelato a quick stir with an immersion blender or whisk then process in an ice-cream maker according to the manufacturer’s instructions. The gelato is finished when it is the consistency of soft serve ice cream (about 20-30 minutes) Scoop into a container, place a piece of plastic wrap or parchment paper on the surface and freeze until firm (4 hours minimum)