Step 1
Preheat oven to 425 degrees F (220 degrees C).
Step 2
Cut off ends of russet potatoes stand potatoes on end and peel potatoes from top to bottom with a sharp knife to make each potato into a uniform cylinder. Cut each cylinder in half crosswise to make 6 potato cylinders about 2 inches long.
Step 3
Place potatoes into a bowl of cold water for about 5 minutes to remove starch from outsides; pat dry with paper towels.
Step 4
Place a heavy oven-proof skillet (such as a cast iron skillet) over high heat. Pour in vegetable oil; heat oil until it shimmers slightly.
Step 5
Place potato cylinders with best-looking ends into the hot oil lower heat to medium-high and pan-fry potatoes until well-browned 5 to 6 minutes. Season with salt and black pepper.
Step 6
Flip the potatoes onto the opposite ends. As they cook use a paper towel held with tongs to carefully blot out the oil from the skillet. Add butter and thyme sprigs to skillet.
Step 7
Pick up a thyme sprig with tongs and use it to paint butter over the top of the potatoes. Cook until butter foams and foam turns from white to a pale tan color. Season with more salt and pepper. Pour chicken stock into skillet.
Step 8
Transfer skillet to preheated oven and cook until potatoes are tender and creamy inside about 30 minutes. If potatoes aren't tender add 1/4 cup more stock and let cook 10 more minutes.
Step 9
Place potatoes on a serving platter and spoon thyme-scented butter remaining in skillet over potatoes. Garnish with thyme sprigs. Let cool about 5 minutes before serving.