Courtesy of the internet and tweaked to address some errant sweet potato purchases. The tweaked version was a big hit!

Fills a ~9x13 oval dish.

Base
1 pound purple or white sweet potatoes (about 2 medium)

Filling
2.5 pounds orange sweet potatoes (about 4-5 medium)
1 egg
1/4 cup butter, melted
1/3 cup brown sugar
1 tsp salt
1/4 cup milk or heavy cream

Topping
1/8 cup brown sugar
2 Tbsp flour
1/4 cup melted butter