Preheat the oven to 350°F.
Wash and dry the sweet potatoes. Pierce with a fork so that they do not explode when baking.
Place on a baking sheet and bake for 45 minutes. Pinch the center to test whether they are done. They should not be hard at all.
While the sweet potatoes are baking, heat the coconut oil in a large skillet over medium-high heat.
Add the onion and mushrooms and sauté for 10 minutes.
Add the beans and heat through for a couple of minutes.
Remove the baked sweet potatoes from the oven. Cut lengthwise right down the center so that you have two boat-shaped halves. Scoop out the center and place in a
large bowl. Do this with all the sweet potatoes, reserving their shells.
Mash the sweet potatoes with a potato masher and add the butter, milk, salt, and pepper to taste. Mix well.
Fold in the bean mixture. Taste to see whether you think it needs more salt or pepper.
Evenly divide the mixture among the empty sweet potato shells.
At this point you may refrigerate or freeze the stuffed potatoes; otherwise, place the potatoes on a baking sheet and bake for 20 minutes.