Combine the milk and 3/4 oz of the pureed pumpkin in a bowl. Aerate with a hand blender for 3 minutes, or until it foams up.Combine the ginger beer, remaining pumpkin puree, and lemon juice in a highball glass with ice and stir.Top with the foam and dust with the pumpkin spice.
Pumpkin spice
Combine everything in a small bowl and mix thoroughly.