Preheat your oven to 400 degrees
Add 2 tablespoons of extra virgin olive oil into a large overproof skillet and place over medium heat
Season 3 boneless skinless chicken breasts generously with garlic powder, onion powder, salt and black pepper and place them into the skillet
Cook for 4 minutes on the first side and then flip the chicken over and cook until both sides are golden brown and the chicken is cooked through with an internal temperature of 165 degrees
Transfer the chicken onto a plate and set it aside for now
Add 3 tablespoons of butter into the same skillet that you browned the chicken in and place it over medium heat
Add 3 large thinly sliced yellow onions and cook for 15-20 minutes or until the onions are caramelized
Add 1 3/4 cups of beef stock into the skillet and mix 2 tablespoons of cornstarch with the remaining 1/4 cup of beef stock until smooth
Add the beef stock and cornstarch into the skillet and bring the mixture to a simmer
Simmer for 2-3 minutes or until the sauce begins to thicken
Nestle the chicken into the sauce and top each breast with a large handful of shredded gruyere or provolone
Transfer the skillet into the 400 oven and cook for 5-7 minutes or until the cheese is melted and beginning to brown
Transfer the skillet onto a heat proof surface to cool for 5 minutes before serving
Serve with mashed potatoes, pasta or rice
Store leftovers in an airtight container in the refrigerator and reheat them in an oven proof skillet at 350 degrees for 15-20 minutes