01 - Set oven temperature to 425°F.
02 - Bring a large pot of salted water to a boil. Add potato chunks and cook for 8 minutes until tender but firm. Drain and leave to steam dry in the colander for 2 minutes.
03 - Place duck fat into a large roasting pan and put in the oven for approximately 3 minutes until melted and hot.
04 - Carefully transfer potatoes into the hot duck fat. Toss gently to coat evenly.
05 - Scatter smashed garlic, rosemary, thyme, kosher salt, and black pepper over the potatoes and toss again to distribute.
06 - Roast in the oven for 40 to 45 minutes, turning once halfway through, until deep golden and crispy on all sides.
07 - Remove from oven, transfer to a serving platter, and serve while hot.