Whipped Sweet Potatoes with Pecan Streusel

My mother used to make these when I was little. With a few adaptations, I have made them every year. Note that this recipe is sized to feed a crowd of 16 to 20. I go ahead and make this amount every year because if I didn't, my family would fight over who got the leftovers.

5 lbs jewel yams (sweet potatoes)
1/2 c half-and-half
1/2 c Grade B maple syrup (or Sucanat)
1 tsp vanilla extract
3/4 tsp salt
4 large eggs, lightly beaten
Cooking spray
1/2 c Sucanat or other dark brown sugar
1/4 c butter, softened
1/8 tsp salt
1/2 c white whole wheat flour
1/2 c chopped pecans

Peel the yams, cut them into chunks, and steam them until fork-tender. Let rest until cool enough to handle.

Place steamed yams in the work bowl of a food processor with half-and-half, maple syrup, vanilla, salt and egg (this may have to be done in batches). Puree until smooth. Spoon potato mixture evenly into a 13"x9" baking dish coated with cooking spray.

Combine butter and sugar in a bowl; beat until fluffy. Work salt and half the flour in with your hands, then add more until mixture is the texture of wet sand. It should come together when squeezed but crumble apart very easily. When the texture is right, stir in the pecans. (This streusel can be prepared a couple of weeks ahead and frozen; bring to room temperature before use.)

Sprinkle streusel over whipped yams. (Casserole can be held at this point for 1 day in refrigerator). Bake covered at 375° for 15 minutes. Uncover and bake an additional 25 minutes or until topping is browned.