Preheat your oven to 350°F
Heat a cast iron skillet or heavy bottom pan to medium high heat.
While the pan is heating, in a small bowl, combine the olive oil and french onion soup mix and stir to create a paste and set aside.
1 Tablespoon olive oil, 1 Tablespoon French onion soup mix
Butterfly your chicken breasts then cut them to create a 4 pieces of chicken that are thin.
2 boneless skinless chicken breasts
Dry your chicken with paper towels and rub the paste on all sides of the chicken.
Add the chicken, smooth side down and cook undisturbed for 2-3 minutes until golden brown before flipping and cooking another 2 mintues-3 minutes. Work in batches if necessary to avoid overcrowding your chicken.
Remove the chicken to a plate and set aside. Your chicken will not be cooked all the way through.
Turn the heat down to low and add the butter and brown sugar to the pan until the butter melts.
2 Tablespoons salted butter, 2 Tablespoons light brown sugar
When the butter and brown sugar have melted, add the sliced onions and stir to coat the onions in the butter and brown sugar.
2 large yellow onions
Cover and cook until the onions become soft and are slightly browned, about 10 minutes.
Add the broth and nestle the chicken back into the pan with the onions.
½ cup low sodium beef broth
Move the pan to the oven and cook for 15 minutes until the onions are soft and jammy.
Cover each chicken breast with ¼ cup of cheese and cook for another 5 minutes allowing the cheese to melt and get slightly golden. The chicken should be 165°F.
1 cup Swiss or gruyere cheese
Top with chopped parsley if desired and serve immediately.
2 Tablespoons parsley