Add cooked sweet potato flesh, 1 cup of milk, maple syrup, vanilla extract, cinnamon, freshly grated nutmeg, and salt to a high speed blender. Blend until smooth.
Pour blended ingredients into a small pot and place on a stove set to medium low heat for about 5 minutes, stirring frequently.
While blended ingredients are heating up, use the steam wand on an espresso maker to froth the rest of the milk.
(If you don't own an espresso machine with a steam wand, heat the rest of the milk up with the other ingredients in the small pot for a less frothy beverage, or use a handheld milk frother once all ingredients are heated.)
Once blended ingredients are steaming and milk is frothed, add blended ingredients into a 16 oz serving cup.
If using optional espresso, add to serving cup.
Gently pour frothed milk into serving cup while slowly stirring with a spoon to combine with the blended ingredients, reserving as much froth as you can.
Remove stirring spoon and carefully add the rest of the froth to the serving cup.
Top with a sprinkle of cinnamon.
Enjoy!