Preheat the oven to 425 degrees F. Line a baking sheet with aluminum foil and spray with nonstick cooking spray.
Wash and dry potatoes. Make a series of 1/8-inch slices along the top of each potato, stopping 1/2 inch from the bottom.
Stir together all of the Herb Butter ingredients. Brush the potatoes all over (including the bottoms), and in between the slices with half of the Butter.
Bake sweet potatoes on prepared baking sheet for 40 minutes then remove from oven. Reheat butter if necessary then brush all of the remaining Butter all over sweet potatoes, including in between slices (I use a fork to fan out the slices).
Return to oven and bake another 10-20 minutes OR until the center potato slices are very tender. Brush baked potatoes with any remaining butter that has accumulated at the bottom of the pan.