Cut the ends off the potatoes, then slice a base off the bottom for a stable base for slicing. Place a potato between two chopsticks and make 1/8" cross slices being careful not to slice all the way through.
Make the brown butter: Heat the butter and thyme in a small saucepan on medium. Cook until the butter is beginning to brown (about 5 minutes).
Place the potatoes in a parchment paper lined baking dish. Brush half of the brown butter and thyme on the potatoes inside the slices and season with salt & pepper.
Bake for 20 minutes, then brush the remaining brown butter on the potatoes.
Bake for another 20 to 25 minutes or until the potatoes are beginning to crisp and are cooked through (depends on the size of your sweet potatoes)
Serve hot and garnish with sour cream or other baked potato toppings.