Prep and preheat: Heat the oven to 375°F (190°C).
Lightly grease a 9x13-inch baking dish.
Cook the base: Boil the high-protein pasta in salted water until just shy of al dente. Drain and set aside. If using cauliflower rice, lightly sauté it in a dry pan for 3–4 minutes to release moisture.
Crisp the bacon: In a skillet over medium heat, cook bacon until crisp.
Transfer to a paper towel to drain. Reserve 1 teaspoon of the bacon fat in the pan (or use oil).
Sauté aromatics and broccoli: Add oil (or reserved fat), then sauté onion for 3–4 minutes until soft. Stir in garlic for 30 seconds.
Add broccoli florets and cook 3–4 minutes until bright and slightly tender. Season with a pinch of salt and pepper.
Make the ranch sauce: In a bowl, whisk Greek yogurt (or cottage cheese), chicken broth (or milk), all ranch spices, and Parmesan. The mixture should be pourable and creamy.
Adjust salt and pepper to taste.
Combine the filling: In a large bowl, add cooked chicken, pasta (or rice/cauli rice), sautéed vegetables, and half the crumbled bacon. Pour in the ranch sauce and fold gently to coat everything evenly.
Assemble: Transfer the mixture to the prepared baking dish. Sprinkle shredded cheddar evenly over the top.
Finish with the remaining bacon.
Bake: Bake uncovered for 18–22 minutes, until the cheese is melted and bubbling at the edges. If you want extra color, broil for 1–2 minutes at the end, watching closely.
Rest and garnish: Let the casserole rest for 5–10 minutes so it sets. Garnish with chopped parsley or chives.
Serve warm.