Preheat the oven to 375°F.

Cook pasta according to package instructions. Set aside.

In a large skillet, cook the bacon until crispy. Remove the bacon from the pan and set aside.

Add the onion and garlic to the bacon drippings and cook until slightly softened. Add cream cheese, milk, ranch seasoning mix, and 1 cup of the mozzarella; stir until smooth. Remove from the heat.

In a large bowl, stir together the ranch mixture, cooked pasta, chicken, pimientos, green onion, and spinach until well combined and place in a 13" X 9" casserole dish. Sprinkle bacon and remaining mozzarella on top.

Bake for 25-30 minutes and until top is golden brown.