Preheat the oven to 350 degrees.
Using a fork, poke holes in the sweet potatoe(s). Wrap individually in tin foil & place on a baking sheet. Bake for 1 hour.
Let cool until they have cooled enough to handle. Remove the tin foil & split down the middle.
In a skillet, melt a couple tablespoons of butter. Throw in some chopped pecans (about 2oz for 4 sweet potatoes) & cook for 3 minutes, stirring often. Mix in a couple tablespoons of brown sugar, and cook for an additional 2 minutes, stirring. Remove from the heat.
Stuff mini marshmallows into the sweet potatoe(s) - really cramming them in - until halfway full. Top with the brown sugar pecans. Finish off with more mini marshmallows, packing them in as well.
Bake for about 15 minutes on 350 degrees, or until the top of the marshmallows are lightly browned.