Bring a large pot of salted water to a boil. Add macaroni and cook just until al dente, 5 to 6 minutes. Drain; return macaroni to the pot.

Stir in cream cheese, 4 tablespoons butter, milk, and powdered cheese packets included in mac and cheese box until well combined. Stir in sour cream, 3/4 cup Cheddar cheese, and ranch mix until combined. Add in chicken, broccoli, and bacon. Reserve 2 tablespoons green onions and stir in remaining green onions. Pour mixture into a lightly greased casserole dish and sprinkle with remaining cheese.

Melt remaining butter and add to a small bowl with panko and pepper. Stir to combine and sprinkle mixture evenly over casserole.

Bake in the preheated oven until bubbly and lightly browned, 20 to 25 minutes. Sprinkle with reserved green onions.