Start by piercing the chicken breasts with a fork 10–15 times on each side. This helps the Italian dressing seep in. Pour the dressing over the chicken in a bowl or ziplock bag and refrigerate for at least 2 hours — overnight if possible — for maximum tenderness and flavor.
Preheat your oven to 400°F (200°C). Heat oil in a skillet over medium-high heat. Add the marinated chicken and sear for about 5 minutes per side, until golden brown. Remove from the pan and set aside.
In the same skillet, lower the heat and melt the butter. Add sliced mushrooms and onions. Sauté for 5–7 minutes, stirring occasionally, until they’re soft and golden. This step builds that rich, restaurant-quality base flavor.
Pour a few tablespoons of water into the skillet to loosen any browned bits stuck at the bottom. Sprinkle in black pepper, garlic powder, onion powder, and salt. Stir everything together to coat the vegetables evenly with the seasoning.
Push the veggies to the sides of the skillet, return the seared chicken to the center, and spoon the mushrooms and onions over the top. Lay slices of Monterey Jack cheese on each chicken breast. Transfer the skillet to the oven and bake for 10 minutes, or until the chicken reaches 165°F internally and the cheese is melted and bubbly.
Once baked, spoon the flavorful pan juices over the chicken to keep it moist and glossy. Serve hot and watch how quickly it disappears!