4 Medium Boneless Chicken Breast (650-700 grams in total)
3 cups Thinly sliced Yellow onion
3 tablespoon Butter
1 tablespoon Olive Oil
½ tablespoon Minced Garlic
2 sprigs Thyme
1 bay leaf
½ cup Dry white wine
1 tablespoon Flour
1 cup Beef Broth
1.5 cup Gruyere cheese
½ teaspoon Pepper
Salt to taste
Preheat the oven to 350 F / 180 C. You will need to bake at the end. Pat dry chicken breast. Using a meat mallet pound Chicken to even thickness. Lightly season with salt and pepper on both sides.
In a large oven-proof skillet, heat 1 tablespoon olive oil and 1 tablespoon butter. When butter starts to foam, sear chicken breast for 3 minutes on each side.
Remove chicken breast from the skillet and keep it loosely covered with foil while doing the rest of the steps. To the same skillet heat remaining 2 tablespoons of butter.
Add sliced onion. Saute for 7-8 minutes. Add a pinch of salt and cook on low-medium heat for another 25-30 minutes. Keep stirring occasionally to prevent onions from burning.
Meanwhile, Preheat oven to 475 degrees. When the onions are evenly golden brown, add minced garlic, thyme, and bay leaf. Cook it for about 30 seconds until the raw garlic smell is gone.
Deglaze the pan with wine. Scrap the bottom of the pan to remove brown bits. let it simmer for 6-7 minutes for the wine to reduce completely. Once the wine has reduced completely, add flour. Toss to coat and cook for 1-2 minutes, until the raw smell is no more.
Slowly add beef stock to the skillet. Whisk well to make a smooth sauce. Simmer for 2 minutes. Add chicken breast back to the skillet. Top it with cheese, bake for about 10 minutes until chicken is cooked through completely and cheeses are bubbly. Serve with mashed potatoes and greens.