Divide the cinnamon before blending
Put the blender portion of cinnamon beside the other ingredients and keep the finishing portion separate. Use plain pumpkin puree rather than pie filling, which brings its own sweetness and spices. Have both large glasses ready before blending, because the intended thick shake is best poured and served promptly rather than left in the jug while you prepare the table.
Blend briefly and stop to scrape as needed, with the machine off and following its instructions. The written milk amount is intended for this ice-cream mixture; adding a large splash to help a struggling blender also makes a thinner drink. Work within the appliance instructions and leave headroom in the glasses for carrying. Sprinkle the reserved cinnamon over the two finished servings.
