1.Preheat oven to 375°F. Grease a 2 or 2 ½ quart casserole dish (preferably a rectangle or oval so there’s a decent surface area for the topping; I use an 8×11) and set aside. Place the sweet potatoes in a large pot, cover with water, and boil until tender (about 7 minutes, depending on the size). Drain really well and return to the pot. Add butter, milk, cinnamon, brown sugar and salt to the potatoes and mash until smooth. Use a hand mixer, if desired, to make them extra smooth. Taste the potatoes and add additional seasonings, if desired. Transfer the mashed potatoes to the prepared casserole dish. Place in the oven until heated through (if they’re already warm it will only take a few minutes). While the sweet potatoes are heating, prepare the topping.