Preheat the oven to 400°F (200°C).

Arrange the bell peppers, jalapeño, garlic, and red onion on a baking sheet. Drizzle with 1 tablespoon olive oil and season with salt and pepper.

Roast for 25–30 minutes, or until tender and lightly charred. Allow to cool slightly.

Transfer the roasted vegetables to a food processor. Add the lemon juice, lemon zest, smoked paprika, oregano, thyme, olive oil, red wine vinegar, honey, parsley, and red pepper flakes.

Blend until smooth, then divide the mixture evenly between two bowls. Reserve one half for making the sauce.

Season the chicken thighs on both sides with salt and place them in a large zip-top bag or bowl.

Add half of the marinade and turn the chicken until evenly coated. Cover and refrigerate for at least 1 hour, preferably 2–8 hours.

Add the reserved marinade and chicken stock or water to a saucepan. Bring to a boil over medium heat.

Reduce the heat to low and simmer for about 10 minutes, or until slightly reduced and thickened. Whisk in the butter, if using. Taste and adjust the seasoning as needed.

Preheat the oven to 400°F (200°C).

Remove the chicken from the marinade and arrange it skin-side up in a baking dish or roasting pan, leaving space between each piece. Discard the marinade that was in contact with the raw chicken.

Bake for 35–45 minutes, brushing with some of the prepared Peri Peri sauce during the last 10–15 minutes, until the chicken is cooked through and reaches an internal temperature of 165°F (74°C).

For crispier skin, broil for 2–3 minutes, or until lightly charred.

Preheat the grill to medium-high heat.

Remove the chicken from the marinade and discard the used marinade. Grill the chicken, starting skin-side down, turning as needed and brushing with the prepared Peri Peri sauce, until cooked through and the internal temperature reaches 165°F (74°C).

Serve the chicken with the remaining Peri Peri sauce and garnish with fresh parsley, if desired.