Slice your potatoes Hasselback style, cutting slices about ⅛ inch thick without cutting through the bottom of the potato. You can use chopsticks or equal-sized wooden spoon handles to help. (See detailed instructions above). Once sliced, add them to a baking sheet.
Add your butter to a saucepan and melt over medium heat.
Brush the tops of the potatoes with the melted butter. You will have about half left. Leave it in the saucepan and set aside.
Sprinkle the potatoes with kosher salt and black pepper.
Place in the oven and bake for 30-40 minutes.
While they are baking, put the saucepan with the butter back on the heat over low. Add in the chopped garlic.
Let the garlic cook in the butter for about 5 minutes over low. The garlic will not saute, but it will flavor the butter.
Remove the potatoes from the oven and gently (and carefully, they are hot!) fan them out a little bit further.
Brush (or pour) the garlic butter over the potatoes making sure to get it in all the cracks and crevices. Place them back in the oven and bake for an additional 10 minutes or until cooked through. You want the edges crispy and the insides fluffy.
Remove from the oven and top with fresh thyme!
Notes
Set your potatoes on chopsticks or equal-sized wooden spoon handles to prevent cutting through the potatoes.