Preheat oven to 350°F (175°C). Grease a 9x13-inch baking dish with nonstick cooking spray or butter.

Bring a large pot of salted water to a boil. Add 12 oz penne pasta and cook for 7 minutes (2 minutes less than package al dente directions). Scoop out 1/2 cup of starchy pasta water, then drain the remaining pasta in a colander.

In a large skillet over medium heat, cook 6 slices of chopped thick-cut bacon for 6 to 8 minutes until crisp and browned. Transfer bacon with a slotted spoon to a paper towel-lined plate, leaving 1 tablespoon of rendered bacon grease in the skillet.

Add 3 minced garlic cloves to the skillet with the bacon grease. Sauté over medium-low heat for 1 minute until fragrant.

Reduce heat to low. Add 8 oz softened cream cheese, 1 oz dry ranch seasoning mix, 1 cup heavy cream, 1/2 cup chicken broth, 1/2 cup reserved pasta water, and 1/4 tsp black pepper. Whisk continuously for 3 to 4 minutes until the cream cheese melts into a smooth, bubbling sauce.

Remove skillet from heat. Stir in 1.5 lbs cooked shredded chicken, half of the cooked bacon bits, 1 cup of shredded sharp cheddar cheese, and the drained penne pasta until thoroughly coated.

Pour the mixture into the prepared 9x13-inch baking dish and spread into an even layer.

Sprinkle the remaining 1 cup of shredded sharp cheddar cheese and the rest of the cooked bacon bits evenly over the top.

Bake uncovered at 350°F (175°C) for 18 to 20 minutes until the cheese is melted and edges are bubbling gently.

Remove from oven and let rest for 5 minutes before topping with 2 tbsp sliced green onions and serving.