01 - Preheat oven to 375°F. Grease a 9x13-inch baking dish with butter or cooking spray.
02 - Bring a large pot of salted water to boil. Cook pasta according to package directions until al dente. 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. Add minced garlic and cook 1 minute until fragrant.
04 - Add cooked chicken, crumbled bacon, thawed peas, salt, pepper, smoked paprika, and dried thyme to the skillet. Stir well and 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 smooth and creamy.
06 - Add the drained pasta and chicken-vegetable mixture to the cheese sauce. Stir until everything is evenly coated and combined.
07 - Pour the mixture into the prepared 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 cheddar cheese. Mix until breadcrumbs are evenly coated.
09 - Sprinkle the breadcrumb mixture evenly over the casserole. Bake for 25-30 minutes until bubbly around edges and golden brown on top.
10 - Remove from oven and let cool for 5 minutes before serving to allow the casserole to set for easier scooping.