Make the spinach filling: Heat your cast iron skillet (or largest oven safe skillet) over medium heat, add the 1 tablespoon olive oil, onion, and a pinch of salt and pepper. Cook, stirring occasionally until the onion is soft and golden brown, about 10 minutes. If the onion ever looks too dry, add in a few tablespoons of water to the skillet to help it soften and caramelize. The water will evaporate as it continues to cook. When the onion is soft, add in the garlic and cook another 30 seconds until fragrant. Then add in the fresh spinach, season with more kosher salt + pepper, and cook until wilted, about 60-90 seconds. Spoon the mixture into a bowl and set aside. Clean your cast iron skillet out with a paper towel.

Prepare the chicken breast: After pounding them to an even thickness, use a knife to cut a large pocket into the middle, having the opening only be on one side of the chicken. (see recipe video to see how I did this). Season both sides of the chicken breast with with kosher salt and black pepper.

Set up the dredging station: Get 2 shallow bowls (or plates) wide enough for the chicken breast to easily fit. (I love using these glass meal prep containers.) In one bowl, add the beaten egg. In the other bowl, combine the pork rind panko and grated parmesan cheese. Mix the pork rind panko and parmesan cheese together.

Stuff and bread the chicken: In each chicken breast, add in 2 of the slices of brie cheese and top with 1/4 of the spinach + onion mixture. Then, dip each chicken breast in the egg wash, then dredge in the pork panko + parmesan mixture. Gently press to adhere. Set on a plate.

Cook the chicken breasts: In the same cast iron skillet over medium heat, add 2 tablespoons of olive oil. Cook the chicken breasts for about 5-7 minutes on the first side until golden brown. Flip, and transfer the skillet to a 400°F oven to finish cooking, another 10-15 minutes until the chicken has an internal temperature of 165°F. Remove from the oven.

Serve: Serve warm. I love serving mine with cauliflower rice risotto (I added in 2 cups of chopped spinach to it, yum!)

Leftovers: Leftovers will keep in an airtight container refrigerated for at least 5 days.

More Info: See the Notes below for more tips, FAQs and substitution options!