Melt and cool the Unsalted Butter (1 tablespoon).
In a blender, combine whole Milk (1 cup), Large Egg (2) and 1 tablespoon of cooled, melted butter. Blend until combined.
Add the All-Purpose Flour (1 cup), Salt (1 pinch), Ground Cinnamon (1/2 teaspoon), and Pure Vanilla Extract (1/2 teaspoon) to the blender. Blend until smooth and frothy.
Preheat oven to 450 degrees F (220 degrees C). Preheat oven after the mixture is blended - this allows for the flour to absorb some of the liquid, which will improve the texture.
Once the oven is preheated, place muffin or popover tin in the oven for 2 minutes to heat up. Remove tin from oven and brush each cup with the Vegetable Oil (2 tablespoon).
Give the batter one more whiz with the blender. Pour batter into each cup, filling about ½ of the way full. Place in preheated oven and bake for 15 minutes. DO NOT OPEN OVEN DOORS DURING THIS TIME.
Reduce oven temperature to 350 degrees F (180 degrees C) and continue to bake for 15 minutes until they are golden brown and dry to the touch. You can open the oven doors during this time.
While they are baking, combine Granulated Sugar (1/2 cup) and Ground Cinnamon (1 1/2 teaspoon) in a pie plate or bowl and set aside.
Remove from oven and empty popovers onto a wire rack and with a sharp paring knife, pierce the bottom of each popover so the steam inside can escape.
Cool until they can be handled but still warm. Brush each popover with melted butter and then roll in the cinnamon and sugar, coating each popover.
Enjoy immediately. They can be rewarmed in a 350 degree F (180 degrees C) oven for about 5-8 minutes.