Preheat oven to 375°F and grease a 8-inch square baking dish or small casserole.
Drain most of the liquid from sweet potatoes. Pour sweet potato chunks in casserole prepared dish.
Dot with butter and sprinkle with brown sugar.
Bake for 45 minutes.
Top with marshmallows and return to oven until they are golden brown, about 5-10 minutes.
Serve warm and refrigerate leftovers.
Notes
You can use mini marshmallows or the bigger ones, they both work great.If you prefer to use fresh sweet potatoes instead of canned yams, cook them first. You can pierce the skin and cook them in the microwave like you would a baked potato or peel them and boil them. Either way, you will want to remove the skin and cut them into large chunks.