Preheat your oven to 400°F (about 200°C) and grease your casserole dish with nonstick spray. While the oven heats, cook the pasta in salted water until al dente, then drain and set aside.
In your blender, combine the cottage cheese, Greek yogurt, ranch seasoning, and hot sauce. Blend until it's smooth and creamy. Then transfer to a bowl, stir in half the mozzarella and cheddar, and fold in the pasta and shredded chicken until everything is coated.
Pour the pasta and sauce mixture into your prepared baking dish. Sprinkle the remaining cheeses evenly over the top. Bake for about 15 minutes, until the cheese is melted and bubbly. After baking, scatter chopped green onions on top and serve.