In a medium bowl, combine the ricotta, 1/2 cup freshly grated parmesan, chopped spinach, 1 minced garlic clove, Italian seasoning, red pepper flakes, and ground nutmeg. Mix until well combined and set aside. I like to chop the spinach finely and squeeze out any excess moisture before mixing—this prevents the filling from becoming watery during baking.
Preheat your oven to 425°F. While it heats, pat the sliced chicken cutlets dry with paper towels, then season both sides generously with salt, pepper, and the 2 minced garlic cloves. Dry chicken ensures better browning when it hits the hot pan.
Heat the extra virgin olive oil in a large oven-safe skillet over medium-high heat until shimmering. Working in batches if necessary to avoid crowding, sear the seasoned chicken cutlets for 2-3 minutes per side until golden brown. This develops a flavorful crust and helps keep the chicken moist during baking. Transfer the seared chicken to a plate.
Return all chicken cutlets to the skillet (it's okay if they slightly overlap). Spread the spinach-ricotta filling evenly over each piece, then top with the marinara sauce, making sure each cutlet is covered. Transfer the skillet to the preheated 425°F oven and bake for 18-20 minutes until the chicken reaches an internal temperature of 165°F.
Remove the skillet from the oven and sprinkle the remaining 1/2 cup freshly grated parmesan over the top of each cutlet. Return to the oven for 2-3 minutes until the cheese is melted and bubbly. Remove from heat and let rest for 5 minutes before serving—this allows the juices to redistribute, keeping the chicken tender and juicy.