Preheat oven to 400 degrees F.

Heat a large ovenproof skillet over medium-high heat (I used a 12-inch cast iron skillet).

Peel the potatoes; cut off the round ends. Slice potatoes into 1-inch thick slices. Pat potatoes dry with a paper towel.

Add the oil and 4 tablespoons of the butter to the hot skillet. Sprinkle potatoes with a pinch of kosher salt and some coarse pepper.

Place the potatoes in the skillet and sear for about 4 minutes, or until they are a nice golden brown. Turn the potatoes and remove from the heat.

Cut the remaining butter into cubes; set aside.

Pour in the chicken stock in the pan. Add the thyme and the garlic. Top the potatoes with the cubed butter.

Place the skillet in the oven and bake for about 30 minutes, or until the potatoes are fork tender. Spoon sauce over potatoes.