Cook the pasta in a pot of salted boiling water until tender. Drain and set aside.
Meanwhile, whisk together the butter and cream cheese in a large pan on medium heat until smooth (it may take a few minutes, just keep whisking!).
Gradually pour in the milk and ranch dressing mix and whisk until smooth and thickened, then stir in the cream of chicken soup. Add the mozzarella to the pan and stir until melted.
Add the pasta and cooked chicken to the ranch alfredo sauce and season with salt and pepper to taste. Pour mixture into a 9x13 casserole dish and top with the crumbled bacon and tater tots in a single layer.
Bake casserole for 28 to 32 minutes, or until the tots are golden brown and crispy and the center of the casserole is bubbly. Top with sliced green onions and any other optional toppings you desire. Enjoy!
Notes
To make the tater tops extra crispy, bake them on a sheet pan for 15 minutes prior to topping the casserole. Finish baking on top of the casserole.