Step 1

Preheat oven to 375°F. Grease a 2 or 2 1/2 quart casserole dish (preferably a rectangle or oval so there's a decent surface area for the topping; I use an 8xand set aside.

Step 2

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.

Step 3

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.

Step 4

In a medium bowl, combine butter, brown sugar, flour, cinnamon and salt (I use a fork or rubber spatula to stir and mash the mixture), then mix in pecans.

Step 5

Remove the sweet potatoes from the oven. Top with half the marshmallows, then sprinkle half the streusel over the marshmallows (pinching pieces together with your fingers). Top with the other half of the marshmallows and sprinkle the remaining streusel over the top. Place back into the oven for 8-15 minutes, until the topping is bubbly and golden brown (keep an eye on it so the marshmallows don't burn). You can also place it under the broiler very briefly to add a little more color to the marshmallows. Note: the longer it is in the oven the more likely that the marshmallows will begin to melt. Allow to sit at room temperature for several minutes before serving.