Step 1: Cook the Pasta and Season the Chicken
Preheat your oven to 375°F (190°C). Bring a large pot of generously salted water to a boil. Cook the pasta according to package directions until just al dente (it will cook more in the oven). Drain and return to the pot. Toss with 1 tablespoon of butter to prevent sticking. While pasta cooks, pat chicken dry and toss in a bowl with smoked paprika, garlic powder, onion powder, 1 teaspoon salt, and ½ teaspoon pepper.

Step 2: Sear the Chicken
In a large oven-safe skillet or Dutch oven, heat olive oil and 1 tablespoon of butter over medium-high heat. Add the seasoned chicken in a single layer (work in batches if needed) and cook without moving for 3-4 minutes to get a good sear. Stir and continue cooking until just cooked through, about 5-7 minutes total. Remove chicken to a plate.

Step 3: Build the Sauce in the Same Pot
In the same skillet over medium heat, melt the remaining 2 tablespoons of butter. Add the BBQ sauce, milk, sour cream, condensed cheddar soup, Dijon mustard, Worcestershire sauce, and cayenne (if using). Whisk continuously until the mixture is completely smooth, hot, and just beginning to simmer. Remove from heat.

Step 4: Combine the Triple Threat
Add the drained pasta, seared chicken (and any accumulated juices), and all three types of shredded cheddar cheese (reserving ½ cup of the blend for topping) to the skillet with the sauce. Gently fold everything together with a large spatula until the pasta and chicken are evenly coated and the cheese is beginning to melt into the warmth of the sauce.

Step 5: Transfer and Top for Baking
If your skillet is not oven-safe, transfer the mixture to a greased 9×13-inch baking dish. Smooth the top. Sprinkle the reserved ½ cup of cheese blend evenly over the surface. In a small bowl, combine the French fried onions or cracker crumbs with the 2 tablespoons of melted butter. Sprinkle this buttery crunch mixture evenly over the cheese.

Step 6: Bake to Bubbling, Golden Perfection
Bake, uncovered, for 25-30 minutes, or until the casserole is bubbling vigorously around the edges, the topping is a deep golden brown, and the cheese on top is fully melted. If the top is browning too quickly, tent loosely with aluminum foil.

Step 7: Rest, Garnish, and Serve
Remove the bake from the oven and let it rest for 10-15 minutes. This crucial step allows the sauce to thicken and set, ensuring clean slices/scoops instead of a runny mess. Garnish with fresh chives or parsley. Serve directly from the skillet or baking dish.