Boil sweet potatoes in large pot with water covering over them by one inch.
Boil about 45 minutes or until fork inserts easily and potatoes feel very soft.
Drain potatoes and pour cool water over them. Allow to cool to touch.
Squeeze out of skins into large mixing bowl. Add remaining ingredients (in the puree ingredients only, not the topping ones!) and whip with mixer until very smooth.
Spoon into greased or sprayed 9 x 13 baking dish.
DIRECTIONS FOR TOPPING:
Put all ingredients into bowl. Smoosh with fingers until all are mixed together well. Mixture should resemble coarse crumbs. Sprinkle over top of puree. Bake for 45 minutes.
Optional: After baking, top with mini-marshmallows and broil just until marshmallows turn brown, about 1-2 minutes under broiler.
Recipe by Dishin & Dishes at https://www.dishinanddishes.com/sweet-potato-casserole-with-pecan-streudal/