01 -
Preheat oven to 375°F. Grease a 2 or 2 1/2 quart casserole dish (preferably rectangular or oval). Set aside.
02 -
Place sweet potatoes in a large pot, cover with water, and boil until tender (about 7 minutes). Drain well and return to the pot.
03 -
Add butter, milk, cinnamon, brown sugar, and salt to the potatoes. Mash until smooth. Optionally, use a hand mixer for extra smoothness. Taste and adjust seasonings, if needed.
04 -
Transfer the mashed potatoes to the prepared casserole dish. Place in the oven until heated through (a few minutes if already warm).
05 -
In a medium bowl, combine butter, brown sugar, flour, cinnamon, and salt. Mix in the chopped pecans.
06 -
Remove casserole from the oven. Top with half of the marshmallows, then sprinkle half of the streusel on top. Add the remaining marshmallows and streusel.
07 -
Return casserole to the oven for 8-15 minutes, until the topping is bubbly and golden brown. Optionally, broil briefly for added color to the marshmallows. Allow to cool slightly before serving.