Step 1: Prepare the Chicken

1. Pat the chicken breasts dry with paper towels to remove excess moisture.
2. Season both sides of the chicken evenly with salt, black pepper, oregano, and smoked paprika (if using). Drizzle with olive oil and rub the seasoning into the meat.
3. Place the seasoned chicken in a large resealable plastic bag or shallow dish.

Step 2: Make the Salmoriglio Sauce

1. In a small mixing bowl, whisk together the olive oil, lemon juice, lemon zest, minced garlic, parsley, oregano, Dijon mustard (if using), salt, black pepper, and red pepper flakes (if using).
2. Reserve half of the sauce for serving and use the other half as a marinade for the chicken.

Step 3: Marinate the Chicken

1. Pour half of the salmoriglio sauce over the chicken, ensuring each piece is well coated. Seal the bag or cover the dish and refrigerate for at least 30 minutes or up to 4 hours. Avoid marinating for too long, as the acidity of the lemon juice can start to break down the chicken’s texture.
2. Keep the reserved sauce covered and refrigerated until ready to serve.

Step 4: Grill or Sear the Chicken

1. Preheat your grill to medium-high heat (about 375°F/190°C). Alternatively, heat a large skillet or grill pan over medium-high heat on the stovetop.
2. Remove the chicken from the marinade and let any excess drip off. Discard the used marinade.
3. Grill or sear the chicken for 6-8 minutes per side, or until the internal temperature reaches 165°F (74°C). Cooking time may vary depending on the thickness of the chicken breasts.
4. Transfer the cooked chicken to a plate and let it rest for 5 minutes to retain its juices.

Step 5: Serve

1. Drizzle the reserved salmoriglio sauce generously over the cooked chicken.
2. Garnish with fresh parsley and serve with lemon wedges on the side for extra brightness.