Cook the sweet potatoes by roasting or boiling them. To roast: Preheat the oven to 350° F. Prick the sweet potatoes all over with a fork, then place them on a baking sheet lined with foil and sprayed with cooking spray. Roast in a 350 degree oven for 45 minutes to 1 hour, until soft. Larger sweet potatoes may take longer to cook. To boil: Peel the sweet potatoes and cut them into chunks, then boil them in a large pot with enough water to cover them for 10 minutes until fork tender rather than roasting them in the oven. Drain well then proceed as directed in the recipe.
3 pounds sweet potatoes
If you have roasted the potatoes, let them cool and scoop out the insides into a large bowl. Alternatively, transfer boiled potatoes straight to a large bowl and gently mash. Add the butter, milk, brown sugar, cinnamon, eggs, vanilla, and salt, and mash with a potato masher or beat using a hand mixer until smooth.
4 tablespoons salted butter, 1/3 cup milk, 1/2 cup brown sugar, 1 teaspoon cinnamon, 2 large eggs, 1 teaspoon vanilla extract, 1/2 teaspoon table salt
Spray a 9x13-inch baking dish with cooking spray, then transfer the mashed sweet potatoes to it and smooth them out evenly using a rubber spatula.
In a separate bowl, combine the brown sugar, flour, cinnamon, salt, melted butter, and chopped pecans. Mix them together with a fork, then sprinkle over the top of the mashed sweet potatoes.
1/2 cup brown sugar, 1/2 cup all-purpose flour, 1/2 teaspoon cinnamon, Pinch of salt, 6 tablespoons salted butter, 1 1/4 cups chopped pecans
Increase the oven temperature to 375° F. Bake the sweet potato casserole for 25-30 minutes, until heated all the way through and the topping begins to brown.
Remove the sweet potato casserole from the oven and sprinkle with the marshmallows. Set the oven to broil, then return the casserole to the oven and cook just long enough for the marshmallows to toast on top. Watch carefully as this can happen very quickly.
2 cups miniature marshmallows
Serve immediately.