In a medium mixing bowl, combine the butter, brown sugar, water, pumpkin pie spice, vanilla and salt. Whisk until the ingredients are well blended.
Place the diced sweet potatoes in the bottom of the slow cooker.
Pour the brown sugar mixture over the sweet potatoes. Gently toss until all of the sweet potatoes are fully coated.
Cook on high for 3 1/2 - 4 hours, stirring occasionally.
When cooking time is complete, stir until the sweet potatoes have a mashed texture. Top the sweet potatoes with the pecans and marshmallows and cook for an additional 10 minutes.
Do not add the marshmallows until ready to serve, they tend to disappear after sitting for a while.
When cooking time is complete, use a serving spoon to scoop servings from the slow cooker directly.
Notes
Be sure to dice your potatoes 1/2 -1 inch thick, they will cook best the thinner you dice them.When adding the mini marshmallows and pecans, be sure not to stir the dish again, you want your marshmallows melted on top of the souffle, covering the dish like a blanket.If you are cooking for someone with a nut allergy, be sure not to include the pecans!Can I make this in advance? Since this is a dish that is typically made for holidays, you might want to make it ahead so that you have less to do when the big day comes. This recipe can easily be made a day in advance, although I have found the best way to make it early is to prep everything the night before and set it up in the morning to cook or even dicing the sweet potatoes and putting them in a ziplock bag can save tons of time on the big day.How can I make this vegan?You can make this vegan but substituting the butter with vegan butter or margarine. Though you will have to skip the marshmallows for they are not vegan.I don't have pumpkin pie spice, what can I use?Use 2 tsp. cinnamon, 3/4 tsp. nutmeg and a 1/4 tsp. cloves in place of pumpkin pie spice in this recipe.