In a medium mixing bowl, combine the wilted chopped spinach, ricotta cheese, softened cream cheese, grated parmesan, minced garlic, red pepper flakes, and salt. Stir vigorously until thoroughly blended and creamy.

Place chicken breasts flat on a clean cutting board. Using a sharp chef knife, carefully slice a horizontal pocket into the thick side of each breast, cutting about 3/4 of the way through without cutting through the opposite edge or back.

Spoon 2 to 3 tablespoons of the spinach ricotta mixture snugly into each pocket. Secure the open seam with 2 wooden toothpicks if desired.

Season both outer sides of the stuffed chicken breasts generously with paprika, garlic powder, dried oregano, sea salt, and black pepper.

Heat olive oil and butter in a large oven-safe cast iron skillet over medium-high heat until hot and shimmering.

Carefully add stuffed chicken breasts to the skillet. Sear undisturbed for 5 to 6 minutes until the bottom achieves a deep golden-brown crust. Gently turn with tongs and sear the second side for 4 to 5 minutes.

Transfer skillet to a 375°F (190°C) preheated oven for 10 to 12 minutes, or cover with a lid over low stovetop heat, until internal temperature reaches 165°F (74°C). Rest 5 minutes before slicing on a bias.