Preheat your oven to 425°F (220°C). Position an oven rack in the middle of the oven to encourage even cooking. Prepare a large rimmed roasting pan or baking sheet, approximately 13 x 18 inches (33 x 46 cm). A lightly oiled metal pan works particularly well for developing browned potato edges. Make sure the pan is large enough to hold the chicken and potatoes in a relatively even layer without excessive crowding.
Remove 6 bone-in, skin-on chicken thighs (about 2 1/2 pounds / 1.13 kg total) from their packaging. Pat the chicken thoroughly dry with paper towels, paying particular attention to the skin. Dry skin is important because surface moisture must evaporate before browning can begin. Trim away any large, loose pieces of excess fat, but leave the skin intact. Set the chicken aside on a clean plate while preparing the remaining ingredients.
Wash and thoroughly dry 1 1/2 pounds (680 g) baby potatoes. Leave very small potatoes whole and halve larger potatoes so the pieces are relatively uniform. Place the potatoes in a large mixing bowl. Add 1 tablespoon (15 ml) of the olive oil, 1/2 teaspoon (3 g) of the fine sea salt, and 1/4 teaspoon (0.5 g) of the freshly ground black pepper. Toss until the potatoes are evenly coated. The surfaces should look lightly glossy rather than heavily coated in oil.
In a small bowl, combine: The remaining 3 tablespoons (45 ml) extra-virgin olive oil 6 garlic cloves (about 18 g), finely minced 1 tablespoon (about 3 g) finely chopped fresh rosemary 1 tablespoon (about 3 g) finely chopped fresh thyme 1 teaspoon (2 g) paprika The remaining 1 teaspoon (6 g) fine sea salt The remaining 1/4 teaspoon (0.5 g) freshly ground black pepper 2 tablespoons (30 ml) freshly squeezed lemon juice Stir until the herbs, garlic, and seasonings are evenly distributed. The mixture should look like a loose, aromatic dressing with visible flecks of herbs and paprika. Stir again immediately before using because the lemon juice and oil may separate.
Place the chicken thighs in a large bowl or on a clean work surface. Spoon the garlic-herb mixture over the chicken, distributing it evenly among the pieces. Rub the mixture over the tops and sides of the thighs. Gently work a little seasoning underneath the skin where possible without tearing it. Keep the skin covering the meat so it can protect the chicken during roasting. The chicken should be evenly coated, with visible herbs and a light sheen of oil.
Transfer the seasoned potatoes to the prepared roasting pan. Spread them into a single layer, placing the cut sides against the metal pan whenever possible. Arrange the chicken thighs among the potatoes, skin-side up. Leave some space between the chicken pieces so hot air can circulate. Avoid stacking potatoes underneath the chicken, as this can cause them to steam rather than roast. If the pan looks crowded, use an additional rimmed baking sheet rather than piling the ingredients together.
Place the roasting pan on the middle oven rack. Roast at 425°F (220°C) for approximately 45–50 minutes. About halfway through cooking, carefully turn the potatoes with a spatula, keeping the chicken skin facing upward. As the chicken roasts, its skin should gradually become golden brown, while the potatoes develop browned edges and tender centers. Check the chicken with an instant-read thermometer inserted into the thickest part of a thigh without touching the bone. The chicken must reach a minimum internal temperature of 165°F (74°C). Dark meat may become more tender when cooked to approximately 175–185°F (79–85°C), provided it remains juicy. If the chicken reaches its desired temperature before the potatoes are tender, transfer it to a clean plate and continue roasting the potatoes until a fork slides easily through their centers. If the potatoes are browning too quickly, move them toward the center of the pan or loosely cover the most browned areas with foil.
Before removing the pan from the oven, check both components. The chicken skin should be golden, with some darker roasted spots around the edges. The meat should be fully cooked according to the thermometer reading. The potatoes should be tender throughout, with lightly crisp, golden-brown surfaces. If the chicken is cooked but the skin needs additional color, briefly use the oven's broiler while watching closely. Garlic and herbs can burn quickly under direct heat.
Remove the roasting pan from the oven: Allow the chicken to rest for 10 minutes before serving. Resting gives the juices time to redistribute through the meat. The potatoes can remain in the warm roasting pan during this period, where they will continue absorbing some of the savory pan juices. Avoid tightly covering the chicken, which can trap steam and soften the skin.
Arrange the roasted chicken thighs and baby potatoes on a serving platter or individual plates. Spoon a little of the flavorful pan juices over the potatoes, leaving the chicken skin mostly uncovered to preserve its crispness. If desired, sprinkle with 2 tablespoons (about 8 g) finely chopped fresh flat-leaf parsley. Serve with wedges from 1 medium lemon (about 120 g), if using, for a fresh citrus finish. Serve warm while the potatoes are tender and the chicken skin is still crisp.
