Pat duck legs dry. In a small bowl combine kosher salt, sugar and crushed peppercorns. Rub the salt mixture evenly over both sides of each duck leg. Nestle thyme sprigs, rosemary and smashed garlic around the legs in a shallow container. Cover and refrigerate for 12–24 hours.

Rinse and dry

After curing, remove duck legs from the salt mixture, discard herbs and garlic. Rinse each leg under cold water to remove excess salt, then pat completely dry with paper towels. Let sit uncovered in the refrigerator for 1 hour if time allows to dry the skin further.

Cook in fat

Preheat oven to 275°F (135°C). Place duck legs in a single layer in an ovenproof dish or Dutch oven. Pour duck fat over the legs until just covered (about 1–1.5 cups). Add a couple of fresh thyme sprigs for aroma. Cover and bake 2.5–3 hours, until meat is very tender and pulls easily from the bone.

Cool in fat

Let the legs cool in the fat to room temperature. You can store submerged in fat in the refrigerator for up to 1 week. For serving: remove legs from fat, drain gently and reserve fat for pan-roasting potatoes and for frying skin crisp.

Crisp the skin

Shortly before serving, preheat a skillet over medium-high heat. Wipe excess fat from the skin side if necessary, then sear duck legs skin-side down 4–6 minutes until the skin is deeply golden and crisp. Finish in a 400°F (200°C) oven 6–8 minutes if needed to heat through.

Pommes fondantes (pan-roasted potatoes)

Prepare potatoes

Cut peeled potatoes into uniform 2-inch cylinders. Rinse and pat dry. Season each piece with a little salt and pepper.

Brown

Heat a large ovenproof skillet over medium-high heat and add olive oil and 1 tablespoon butter. When foaming, arrange potatoes cut-side down and brown undisturbed 3–4 minutes until well colored. Turn to brown the sides briefly, about 1–2 minutes.

Add stock and finish

Reduce heat to medium, add remaining butter and carefully pour in chicken stock (it will sizzle). Add 1 tsp salt and 1/2 tsp black pepper. Cover and simmer gently 12–15 minutes until potatoes are tender and most stock has reduced. Uncover and baste potatoes with remaining butter; let them finish and develop a glossy, slightly caramelized exterior 3–4 minutes. Keep warm until plating.

Braising jus (boucherie-style pan sauce)

Sweat aromatics

In a medium saucepan or the same skillet used for potatoes (wipe out any burnt bits), add 1 tablespoon duck fat or butter over medium heat. Add minced shallots, diced carrot and diced celery. Sweat gently 5–7 minutes until softened and translucent but not colored.

Build sauce

Stir in tomato paste and cook 1 minute. Deglaze with red wine, scraping up any browned bits. Reduce wine by half, about 2–3 minutes.

Simmer

Add chicken or veal stock, bay leaf and thyme. Bring to a simmer and reduce gently until sauce coats the back of a spoon, about 10–12 minutes. Discard bay leaf and thyme stem.

Finish and mount

Taste and season with 1/2 tsp salt and 1/4 tsp black pepper. Off heat, whisk in cold cubed butter a little at a time to emulsify and give a glossy finish. Keep warm and strain through a fine sieve into a small saucepan if you prefer a smoother jus.

Optional enrich

If you collected any juices while crisping the duck, whisk a tablespoon into the jus for extra richness and meat flavor.

Finish & plating

Assemble

Place 2 pommes fondantes on each plate. Top with a duck leg (bone in) and spoon 2–3 tablespoons of the braising jus around and over the duck. Scatter a small handful of watercress or microgreens beside the duck and garnish with sliced cornichons.

Serve

Serve immediately with a small dollop of grainy Dijon mustard on the plate or on the side. Provide extra sauce for guests as desired.