Step 1: Cook the Pasta and Prepare the Chicken
Bring a large pot of well-salted water to a boil. Cook the pasta according to package directions for al dente (it will continue to cook in the oven). Drain and set aside. While the pasta cooks, season the cubed chicken evenly with garlic powder, onion powder, salt, and pepper. Heat olive oil in a large skillet over medium-high heat. Add the chicken in a single layer and cook for 5-7 minutes, stirring occasionally, until golden brown and cooked through. Remove the chicken to a plate, leaving any juices in the skillet.

Step 2: Build the Flavor Foundation with Bacon and Aromatics
In the same skillet, reduce heat to medium. Add the chopped bacon. Cook, stirring occasionally, until the bacon is crisp and the fat has rendered, about 8-10 minutes. Using a slotted spoon, transfer the crispy bacon to a paper towel-lined plate, leaving about 2 tablespoons of the precious bacon fat in the skillet. To the hot bacon fat, add the diced onion. Cook for 4-5 minutes until softened and translucent. Add the minced garlic and cook for 1 more minute until fragrant.

Step 3: Craft the Creamy Ranch Roux Sauce
Push the onions and garlic to the sides of the skillet. Add the 2 tablespoons of butter to the center and let it melt. Sprinkle the flour over the butter and whisk continuously for 1-2 minutes to form a pale golden roux, cooking out the raw flour taste. Slowly begin to pour in the warm milk while whisking constantly to prevent lumps. Once the milk is incorporated and the mixture begins to thicken, whisk in the entire packet of dry ranch seasoning. Then, slowly whisk in the chicken broth until smooth.

Step 4: Create the Ultimate Cheese Sauce
Bring the sauce to a gentle simmer, whisking frequently. Let it cook for 3-4 minutes until it thickens enough to coat the back of a spoon. Remove the skillet from the heat. It is crucial to take the sauce off the heat before adding the next ingredients to prevent curdling. Whisk in the room-temperature sour cream until fully blended. Then, stir in the shredded sharp cheddar and Monterey Jack cheeses until melted and smooth. The sauce will be luxuriously thick and creamy.

Step 5: Assemble the Casserole
Preheat your oven to 375°F (190°C). In the large pot used for the pasta (or a very large mixing bowl), combine the drained al dente pasta, cooked chicken cubes, most of the crispy bacon (reserve some for topping), and the entire creamy ranch-cheese sauce from the skillet. Gently fold everything together until every piece of pasta and chicken is thoroughly coated. Transfer this mixture to a greased 9×13 inch (23x33cm) baking dish, spreading it into an even layer.

Step 6: Apply the Golden, Cheesy Blanket
In a small bowl, mix the shredded Colby Jack and grated Parmesan cheese. Sprinkle this cheese blend evenly over the entire surface of the casserole, covering it completely. For extra crunch and flavor, sprinkle the reserved crispy bacon bits over the cheese.

Step 7: Bake, Broil, and Rest
Bake the casserole in the preheated oven, uncovered, for 20-25 minutes, or until the cheese is fully melted and the edges are bubbling vigorously. For a spectacular golden-brown, bubbly top, switch the oven to broil for the final 1-2 minutes, watching carefully to prevent burning. Remove the casserole from the oven and let it stand for 10 minutes before serving. This rest period is essential for the sauce to set slightly, allowing for perfect, clean slices