Pat the chicken breasts dry with paper towels and place them on a cutting board.
Using a sharp knife, carefully butterfly each chicken breast by slicing horizontally into the thick side, creating a pocket without cutting all the way through.
Mix lemon juice, minced garlic, chopped thyme, and parsley in a small bowl, then marinate the chicken in this mixture for at least 30 minutes in the refrigerator.
Preheat your oven to 180°C (350°F). While it heats, prepare the stuffing by combining chopped spinach and crumbled feta cheese.
Stuff each chicken pocket with the spinach and feta mixture, pressing gently to pack the filling inside.
Heat olive oil in an oven-safe skillet over medium-high heat until shimmering and slightly fragrant.
Sear the stuffed chicken breasts for 3-4 minutes per side until golden brown and crispy on the outside.
Transfer the skillet to the preheated oven and roast for 15-20 minutes, or until the internal temperature reaches 74°C (165°F).
Remove the skillet from the oven and let the chicken rest for 5 minutes; this helps keep the juices locked in.
Slice the stuffed chicken breasts and serve with a drizzle of pan juices and your favorite sides.
