Preheat your oven to 375°F and grease a 9x13-inch baking dish with butter or cooking spray.

Bring a large pot of salted water to a boil. Add the egg noodles and cook until just al dente, about 6 to 8 minutes. Drain and set aside.

In a large skillet, heat olive oil over medium-high heat. Add the chicken pieces, ranch seasoning, garlic powder, and black pepper. Cook until lightly browned, about 5 to 6 minutes.

In a large mixing bowl, combine chicken broth, sour cream, and cream cheese. Whisk until smooth, then add melted butter and pepperoncini juice; whisk again until well combined.

Add the drained noodles, browned chicken, and sliced pepperoncini to the sauce. Stir gently to coat evenly.

Transfer the mixture to the prepared baking dish and spread evenly. Sprinkle mozzarella and cheddar cheese over the top.

Bake uncovered for 40 to 45 minutes until the top is bubbly and lightly golden.

Let the casserole rest for 5 to 10 minutes before serving.