Preheat oven to 400 degrees F.
Peel the potatoes, rinse with cold water, and pat dry with paper towels. Then slice the ends off the potatoes so they lay flat on either side. Cut them into 2 inch thick slices.
Heat cooking oil in a large cast-iron or oven-safe skillet over medium-high heat.
Place the potatoes cut-side down in a single layer, and cook until golden brown, 6 to 7 minutes. Flip and brown the other side for 4-5 minutes.
Remove the skillet from the heat and drop in butter, thyme, rosemary, garlic, and chicken stock. Season with salt and pepper to taste.
Place in the preheated oven and bake, uncovered until the potatoes are fork-tender and creamy inside, about 30 minutes. If potatoes aren't tender, add 1/4 cup more stock and let it cook for 10 more minutes.
To check if the potatoes are tender, insert a skewer or toothpick in the thickest part of the potatoes it should slide in easily.
Spoon the butter mixture over the cooked potatoes, garnish with parsley, or sprigs of thyme, if desired. Serve warm.