Preheat oven to 350 degrees.

Cut sweet potatoes in half and place cut side up on a baking sheet. Spray with a little oil and bake for 50 to 60 minutes, until fork tender. Remove from oven and let cool. Remove skins and mash finely with a potato masher or food processor. You should have 2 cups mashed sweet potato flesh. Place in a mixing bowl.

Bring to a boil the butter, sugar, broth and salt. With mixer on medium, mix in the broth mixture with the sweet potatoes until smooth. With mixer running, add in chile powder, cumin, masa, tapioca and baking powder a little at a time. Mix until fluffy, about 10 minutes on high speed. Let sit 10 minutes on counter to make sure masa is fully hydrated.

Spread ⅓ cup of masa mixture in center of a corn husk, spreading in a square until a little thicker than ¼ inch. Sprinkle about 1 tablespoon of nuts in center. Roll tamale in hands until masa mixture surrounds the nuts. Fold corn husks up at bottom.

Steam tamales until firm, about one hour.

Serve immediately.