Start by peeling and cubing the sweet potatoes into uniform pieces, about 1-inch thick.
Place the cubed sweet potatoes at the bottom of the slow cooker. Add the butter (or vegan substitute), brown sugar (or maple syrup if using), salt, pepper, cinnamon, and nutmeg.
Pour the vegetable broth over the sweet potatoes.
Cover the slow cooker and set it on low for 6-8 hours or high for 3-4 hours.
Once cooked, you can either mash the sweet potatoes directly in the slow cooker or serve them whole.