Add the melted butter/oil to the bottom of a large baking pan. Add the halved potatoes and toss with the thyme, salt, and generous pepper, to coat well with the butter/oil.
Realign the potatoes with cut sides down and thyme distributed though-out.
Bake for 30 minutes.
Next increase the heat to 450°F for a final 15 minutes to crisp the potatoes to a golden hue.