Preheat and set up: Preheat your oven to 230°C / 450°F (fan 220°C). Place a large rimmed baking sheet in the oven to heat (this helps the fries start crisping the moment they hit the pan). High initial oven heat is essential for browning and crisping — it gives the fries a seared exterior instead of slow steaming.

Prep the potatoes: Peel (optional) and cut potatoes into 1‑cm / 3/8" thick batons for fries. Put them in a large pot, cover with cold water, add 1 tsp salt, and bring to a gentle boil. Par‑boiling (6–8 minutes, until just tender at the edges but not falling apart) removes surface starch and starts cooking the inside — this is key for a crispy exterior later.

Rough and dry the fries: Drain the par‑boiled potatoes and return them to the hot pot on the stove for 30–60 seconds with the lid off. Shake the pot gently (or toss with a spoon) to rough up the surfaces — these nicks and roughed edges increase surface area so the fries crisp better. Transfer to a tray and pat completely dry with kitchen towels; moisture prevents browning.

Season the fries: Toss the dried potatoes with 2 tbsp olive oil, 1 tsp smoked paprika, 1/2 tsp kosher salt and a few grinds of black pepper. The oil conducts heat and the paprika adds a smoky depth that elevates simple fries to bistro quality.

Roast the fries (first roast): Spread the fries in a single layer on the preheated baking sheet (use parchment or a light coating of oil if needed). Roast for 20 minutes, then remove and flip or shake the pan to turn them. Return to the oven for another 10 minutes until starting to color. This two‑stage roast (flip halfway) encourages even browning.

Season the chicken: While the fries start roasting, pat the chicken thighs very dry with paper towels (dry skin crisps better). Season both sides generously with kosher salt, black pepper, a pinch of smoked paprika and the dried thyme (or tuck fresh thyme under the skin). Let sit at room temperature for 10 minutes — this helps them sear evenly.

Sear the chicken: Heat a large ovenproof skillet (cast‑iron preferred) over medium‑high heat until very hot. Add 2 tbsp olive oil. Place the chicken thighs skin‑side down and press gently so the skin contacts the pan; cook undisturbed 6–8 minutes until the skin is deep golden and most of the fat has rendered. Searing at high heat creates the Maillard crust that gives flavor and texture.

Finish in the oven: Flip the thighs skin‑side up, add 1 tbsp butter and transfer the skillet to the oven (alongside the fries if there is space; lower rack for fries). Roast 12–18 minutes — the internal temperature should reach 74°C / 165°F in the thickest part of the thigh. Resting after roasting allows juices to redistribute and keeps the meat juicy.

Crisp the fries (final blast): When chicken has 8 minutes left or is resting (if finished sooner), increase oven to 240°C / 465°F and return fries to the hot sheet for 6–8 minutes to achieve final browning and crispness. The high final blast seals a crunchy exterior.

Sauté the vegetables: While chicken rests and fries brown, wipe out the skillet (reserve a couple tablespoons of chicken fat if present) and return to medium heat. Add 1 tbsp butter, the minced shallot and a pinch of salt; sweat 2 minutes until softened to build a sweet aromatic base. Add garlic and the mixed vegetables, season with salt, pepper and a squeeze of lemon juice, and sauté just until bright and tender‑crisp (3–5 minutes). Quick cooking preserves texture and color.

Make the pan sauce: Push vegetables to the side and add the optional 60 ml white wine or chicken stock to the skillet. Scrape up browned bits (fond) from the pan — that flavor is concentrated and essential. Reduce by half, then whisk in remaining 1 tbsp butter and lemon zest. Taste and adjust seasoning. The butter‑enriched reduction gives a silky, glossy sauce to tie the plate together.

Plate and finish: Pile a handful of fries on each plate, add a bed of sautéed vegetables, and top with a chicken thigh. Spoon pan sauce over the chicken, sprinkle with chopped parsley and a light squeeze of lemon. Serve immediately while skin and fries are still crisp.

Rest and store leftovers: If not serving all immediately, cool leftover chicken and fries on a rack (prevents sogginess) and store separately in airtight containers in the fridge up to 3 days. Re‑crisp fries in a hot oven (220°C / 425°F) for 6–8 minutes.