Preheat oven to 375°F. Cook penne according to package directions; drain, reserving 1 cup cooking water. Place pasta in a large bowl, and set aside.
Heat a large skillet over medium. Add bacon, and cook, stirring often, until crisp, about 5 minutes. Using a slotted spoon, transfer bacon to a plate lined with paper towels. Reserve drippings in skillet.
Add garlic to hot drippings in skillet over medium, and cook, stirring constantly, until fragrant, about 1 minute. Whisk in whipping cream and cream cheese; cook, whisking often, until cream cheese is melted and mixture is smooth, about 2 minutes. Remove from heat, and stir in Parmesan, ranch dressing mix, pepper, and reserved 1 cup cooking water. Pour over pasta. Fold in chicken and 1 cup of the mozzarella cheese. Pour mixture into a lightly greased (with cooking spray) 13- x 9-inch baking dish. Top with bacon and remaining 1 cup cheese.
Bake in preheated oven until golden and bubbly, about 20 minutes. Sprinkle with parsley, and serve hot.