Make the garlic butter: In a small bowl, mash softened butter with minced garlic, parsley, chives, lemon zest, a pinch of salt, and black pepper. Add Parmesan if using. Stir until smooth. If adding spinach, sauté it briefly in a dry pan until wilted, squeeze out moisture, chop, and fold into the butter.

Chill the filling: Spoon the garlic butter onto a piece of parchment or plastic wrap and form it into a small log. Chill in the fridge for 10–15 minutes so it firms up. This makes stuffing cleaner and prevents leaks.

Prep the chicken: Pat the chicken breasts dry. Using a sharp knife, cut a deep pocket into the thickest side of each breast, keeping the opposite side intact. Don’t slice all the way through.

Season well: Mix paprika, onion powder, Italian seasoning, 1 teaspoon salt, and 1/2 teaspoon black pepper. Rub this all over the chicken, including inside the pocket.

Stuff securely: Slice the chilled garlic butter into four equal pieces. Tuck one piece into each chicken pocket. Pin the opening closed with toothpicks, or tie with kitchen twine. Press gently to seal.

Preheat and prep the pan: Heat the oven to 400°F (205°C). Place an oven-safe skillet (cast iron works best) over medium-high heat and add olive oil.

Sear for color: Sear the chicken for 2–3 minutes per side until nicely golden. Handle gently to keep the filling inside. You’re building color, not cooking through.

Bake to finish: Transfer the skillet to the oven and bake for 10–15 minutes, depending on thickness, until the internal temperature reaches 165°F (74°C) at the thickest part.

Rest and serve: Let the chicken rest for 5 minutes. Remove toothpicks. Spoon any pan juices over the top and finish with a squeeze of fresh lemon. Serve with your favorite side.