Prep the oven and pan. Heat the oven to 375°F (190°C). Lightly grease a 9x13-inch baking dish with butter or cooking spray.

Cook the base. Boil the pasta in salted water until just shy of al dente (about 1 minute less than the package suggests). If using potatoes, par-cook them in salted boiling water for 6–8 minutes until barely tender. Drain and set aside.

Crisp the bacon. In a skillet over medium heat, cook the bacon until crisp. Drain on paper towels and crumble. Reserve 1 tablespoon of bacon fat if you want extra flavor in the sauce.

Sauté the garlic (optional). In the same skillet, melt the butter (or use the reserved bacon fat). Add minced garlic and cook 30–60 seconds until fragrant. Remove from heat.

Make the ranch cheese sauce. In a large bowl, whisk together softened cream cheese, sour cream, ranch seasoning, and 1/2 cup broth or milk until smooth. Stir in the sautéed garlic and 1 cup shredded cheddar. If the mixture seems too thick, add a splash more liquid. It should be creamy and spreadable.

Combine the filling. Add the chicken, cooked pasta or potatoes, half of the crumbled bacon, and half of the green onions to the bowl. Fold gently to coat everything with the sauce. Taste and season with salt and pepper.

Assemble the casserole. Spread the mixture evenly in the prepared baking dish. Top with the remaining cheddar and the mozzarella for a nice melt and golden top.

Bake until bubbly. Bake 18–22 minutes, or until the cheese is melted and the edges are bubbling. For extra color, broil for 1–2 minutes at the end, watching closely.

Finish and serve. Sprinkle the remaining bacon and green onions over the top. Let it rest 5 minutes so it sets slightly. Serve warm.