Duck Fat Roast Potatoes
British Style Roast Potatoes in Duck Fat
Crispy outside, fluffy inside — roasted in duck fat with rosemary, thyme, sage, and garlic.
A quick boil in a baking soda bath, roughed edges, and a ripping-hot pan give you shatteringly crisp roast potatoes that actually stay crunchy.
Watch my video to follow along step-by-step.
British Duck Fat Roast Potatoes
Yield 4–6 servings
Time Prep 20 minutes · Cook 50–60 minutes
Equipment
13×9-inch (33×23 cm) Pyrex casserole or heavy metal roasting pan; large pot; colander
Ingredients
Potatoes & Parboil
2 to 2¼ lb (900–1,000 g) floury potatoes, peeled and quartered into large chunks
(UK: Maris Piper/King Edward • US: Russet = crispiest; Yukon Gold = creamiest)Water, to cover
1–2 tsp flaky sea salt (for the boil)
½ tsp baking soda
Bouquet garni: 3–4 sprigs thyme, 1–2 sprigs rosemary, 2–3 sage leaves, 1-2 bay leaves (optional), all tied together
Roasting
⅓ cup (about 75 g) duck fat
4–6 garlic cloves, lightly crushed, skins on
4–6 sprigs thyme
2–3 sprigs rosemary
10–12 whole sage leaves
To Finish
Flaky sea salt, to taste
Freshly cracked black pepper, to taste
Method
1) Heat the dish safely (avoid thermal shock)
Place the cold 13×9-inch Pyrex on a cold oven rack. Add the duck fat.
Set oven to 425°F (220°C) and let the glass and fat come up to temperature together while you parboil the potatoes. The fat should be hot and shimmering.
2) Parboil (salt + baking soda)
Put potato chunks in a large pot and cover with cold water. Add 1–2 tsp flaky sea salt and ½ tsp baking soda.
Add the bouquet garni.
Bring to a boil, then simmer briskly 8–10 minutes until the edges are tender but the centers are still firm when poked with a knife.
Drain well; discard the bouquet.
3) Rough up & steam dry
Return potatoes to the empty hot pot (or leave in a colander over the pot). Shake hard to rough the edges until they look a little fuzzy, not smooth.
Let them steam dry a few minutes until the surfaces look matte, not shiny.
4) First roast (garlic duck fat)
Pull the hot dish/tray from the oven and add the crushed garlic cloves. Carefully add the dry, roughed potatoes into the hot garlic duck fat (it may spit).
Turn to coat every surface.
Roast 20 minutes without touching. This sets the crust on the underside.
5) Turn & add herbs
Remove the dish/tray; turn each potato so a new side sits in the fat.
Add thyme and rosemary sprigs to the dish to perfume the fat.
Roast 15–20 minutes more, turning once if needed, until deep golden and crisp on the edges.
6) Crisp the sage & finish
During the last 5–10 minutes, using a frying or sauté pan over medium high heat, melt 2 Tbs of duck fat, scatter in a few whole sage leaves so they fry in the hot fat.
Lift them out as soon as they’re crisp. Do not blacken them. Drain on some paper towelling.
Pull the dish; remove garlic cloves and spent herb stems.
Shower potatoes with flaky sea salt and black pepper (if using) while hot.
Transfer to a warm platter and scatter the crisp sage on top. Serve immediately.
Why This Works
Baking soda raises pH, loosening surface pectin for more crunch.
Roughing increases surface area for better contact with hot fat.
Preheated duck fat jump starts browning for glassy, crisp edges.
High heat + minimal flips produces even color without steaming.
FAQs
Best potatoes? UK: Maris Piper/King Edward. US: Russet is crispiest; Yukon Gold is creamiest.
No duck fat? Goose fat or beef tallow are excellent; neutral oil works with less flavor.
Make ahead? Parboil, rough, and steam dry earlier in the day. Roast just before serving.
Convection/fan? Try 400°F (200°C) and watch closely near the end.
Herbs? Add rosemary and thyme mid-roast to perfume the fat; finish with crispy sage and flaky salt.
Larder Notes
Glass safety: Pyrex must start cold and heat with the oven. Never move cold glass into a hot oven. A heavy metal roasting pan also works (preheat empty, then add fat).
Salt balance: Season the water well; finish boldly with flaky salt while hot.
Garlic: Whole, skin-on cloves perfume the fat without scorching. Remove before serving unless you like the mellow, soft cloves alongside.
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