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1
Preheat oven to 425 degrees F (220 degrees C).
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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.
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3
Place potatoes into a bowl of cold water for about 5 minutes to remove starch from outsides; pat dry with paper towels.
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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.
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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.
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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.
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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.
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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.
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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.
