4 BONELESS, SKINLESS CHICKEN BREASTS (ABOUT 1 1/2 POUNDS TOTAL)1 TEASPOON KOSHER SALT, DIVIDED 4 OUNCES CREAM CHEESE, AT ROOM TEMPERATURE 2 OUNCES SHREDDED MOZZARELLA CHEESE (ABOUT 1/2 CUP)1 (10-OUNCE) BOX FROZEN SPINACH, THAWED AND SQUEEZED TO REMOVE EXCESS MOISTURE 1/2 SMALL SWEET ONION, GRATED 1 CLOVE GARLIC, MINCED
- Make a pocket in the chicken breasts and season. Place a chicken breast on a cutting board. Press a hand on top of the breast and carefully insert the tip of a chef’s knife into the thickest part of the chicken breast. Cut an opening about 3 inches wide, then cut 3/4 of the way through the breast to create a pocket without cutting all the way through. Repeat with the remaining breasts. Thoroughly dry the chicken on all sides with paper towels. Season with the salt on all sides and inside the pocket.
- Make the filling. Combine the cream cheese, mozzarella, spinach, onion, garlic, and remaining salt in a small bowl and mix until well-combined.
- Stuff the chicken breasts with the filling, spooning a quarter of the filling mixture into each breast.
- Heat the oil over medium-high heat in a large skillet. Heat the oil in a 10-inch or larger skillet (preferably straight-sided and not nonstick; cast iron is a great option) over medium-high heat until shimmering, about 3 minutes.
- Carefully add the chicken to the hot pan and cook for 5 to 7 minutes. Swirl the pan just before adding the breasts to evenly distribute the oil. Carefully add the chicken one at a time and do not touch, poke, or move the chicken for 5 to 7 minutes. If you try to turn the chicken and it feels stuck, it isn’t golden and crispy or ready to flip.
- Flip the chicken and cook until it reaches 165°F, 5 to 7 minutes more. Flip the breasts over and add the butter right between them. Pick up the pan and give it a gentle swirl to distribute the melting butter. Cook until they reach an internal temperature of 165°F, 5 to 7 minutes more.
- Slice and serve. Remove the chicken breasts to a plate or clean cutting board. Let rest for 4 minutes before slicing and serving.