Bring a medium pot of water to a gentle boil and set a large bowl of ice water nearby. Cut the potatoes into classic fries (about 1/2" / 1.2 cm thick sticks). Soak the cut potatoes in cold water for 10–15 minutes to remove surface starch — this helps them crisp in the oven rather than glue together.

While the potatoes soak, pat the chicken breasts dry with paper towels (dry surface = better browning). Season both sides evenly with 1 tsp kosher salt, 1/4 tsp black pepper, the paprika and the dried thyme. Lightly press the seasoning onto the meat so it adheres; this forms the flavor crust during searing.

Par‑boil the fries: drain the soaking water, place the potato sticks in the boiling water and cook for 4 minutes — you want them just starting to become tender at the center, not falling apart. Par‑boiling cooks the interior so the outside doesn't have to stay in the oven forever, which keeps them fluffy inside.

Drain the par‑boiled fries and spread them on a clean kitchen towel or baking sheet to dry thoroughly. Moisture on the surface will steam the fries and prevent crisping, so drying is essential.

Preheat the oven to 220°C (425°F). Toss the dried fries with 2 tbsp olive oil and 1/2 tsp kosher salt on a rimmed baking sheet, arranging them in a single layer with space between pieces. Roast on the top rack for 35–40 minutes, flipping once halfway through, until deeply golden and crisp. High oven heat encourages Maillard browning for a crispy exterior.

While fries roast, heat a large ovenproof skillet over medium‑high heat. Add 1 tbsp olive oil. When it shimmers, add the seasoned chicken breasts, presentation side down first. Sear 3–4 minutes without moving to create a golden brown crust — this crust locks in juices and contributes savory flavor.

Flip the chicken, add the butter and let it melt, spooning it over the breasts for 30–60 seconds to baste (basting adds flavor and helps finish the top). Transfer the skillet to the preheated oven and roast 8–12 minutes, or until the internal temperature reaches 74°C (165°F). Finishing in the oven cooks the chicken evenly without burning the outside.

While the chicken rests, return the skillet to medium heat (careful — handle will be hot). Add the sliced onion and smashed garlic cloves to the pan fat. Cook 6–8 minutes, stirring occasionally, until the onion is soft and beginning to caramelize. Caramelization converts onion sugars into a glossy, savory‑sweet component that balances the savory chicken and fries.

Deglaze the pan with 1/4 cup warm water: pour it into the skillet and scrape up the browned bits (fond) with a wooden spoon. Reduce for 1–2 minutes until slightly thickened, then taste and season with a pinch of salt and pepper. The fond is concentrated flavor — deglazing captures it to make a quick pan sauce.

Slice the rested chicken on a cutting board (resting keeps juices from spilling out) and return slices to the pan briefly to warm and coat in the sauce, about 30 seconds. Resting also allows carryover cooking to finish and the fibers to relax, keeping meat juicy.

Remove fries from the oven when golden and sprinkle with a small pinch of salt. Plate each serving with 150–200 g of fries, one sliced chicken breast portion, and a generous spoonful of the caramelized onion and garlic pan sauce spooned over the chicken. The contrast of textures and the glossy sauce make this feel like a bistro entrée.

Finish (optional): For a bright finish, grate a little lemon zest over the chicken or scatter chopped fresh parsley if available. Acidity and fresh herbs lift the whole plate and provide balance.