Heat the oven: Preheat to 350°F (175°C). Lightly grease a 9x13-inch baking dish.
Cook the base: If using pasta, boil in salted water until just shy of al dente.
Drain well. If using rice or cauliflower rice, have it cooked and ready.
Make the sauce: In a large bowl, beat the softened cream cheese until smooth. Mix in sour cream, 1 1/2 cups shredded cheddar, ranch seasoning, garlic, and 1/2 cup broth or milk.
Stir until creamy. Add more liquid, a splash at a time, until it’s thick but spoonable.
Add the mix-ins: Fold in chicken, half the bacon, green onions, and vegetables if using. Taste and season with salt and pepper.
Remember, ranch and bacon are salty, so go easy.
Combine with base: Gently stir in the cooked pasta or rice until everything is coated. Transfer to the prepared baking dish and spread evenly.
Top it off: Sprinkle the remaining 1/2 cup cheddar over the casserole. Toss crushed crackers or panko with melted butter and the remaining bacon.
Scatter the mixture over the top for a crunchy finish.
Bake: Bake uncovered for 20–25 minutes, until the casserole is bubbly and the topping is golden brown.
Rest and serve: Let it sit for 5–10 minutes to set up. Garnish with extra green onions if you like. Serve warm.