01 - Preheat oven to 375°F. Grease a 9x13-inch baking dish with cooking spray or butter.
02 - Bring a large pot of salted water to a boil. Cook pasta according to package directions until al dente, approximately 8-10 minutes. Drain well and set aside.
03 - Heat a large skillet over medium heat. Add a splash of oil or butter, then sauté diced onion for 3 minutes until softened and translucent. Add minced garlic and cook for 1 minute until fragrant, being careful not to burn.
04 - Add cooked chicken, crumbled bacon, thawed peas, salt, black pepper, smoked paprika, and dried thyme to the skillet with the aromatics. Stir to combine evenly. Remove from heat.
05 - In a large mixing bowl, whisk together sour cream, softened cream cheese, whole milk, and 2 cups shredded cheddar cheese until completely smooth and well combined.
06 - Add the drained pasta and chicken mixture to the bowl with the cheese sauce. Stir thoroughly until all ingredients are evenly coated and distributed throughout the pasta.
07 - Pour the pasta mixture into the prepared 9x13-inch baking dish. Spread evenly with a spatula, ensuring the surface is level.
08 - In a small bowl, combine panko breadcrumbs, melted butter, and remaining 1/2 cup shredded cheddar cheese. Mix well until the breadcrumbs are evenly coated with butter.
09 - Sprinkle the breadcrumb mixture evenly over the top of the casserole. Bake for 25-30 minutes until the cheese is bubbling and the topping is golden brown.
10 - Remove from oven and let the casserole rest for 5 minutes before serving. This allows the sauce to set slightly for easier serving.