Preheat oven to 350F and grease a 9x13-inch casserole dish.
Cook pasta 1 minute less than package directions for al dente and drain, saving 1-2 cups pasta water.
During the time the pasta is cooking, melt butter in a large saucepan with deep sides. Add all-purpose flour and cook and stir for 1 minute over medium heat.
Slowly whisk in half-and-half about ¾ cup at a time. Once all liquid is added, bring to a boil and simmer for 2 minutes, stir regularly.
Add sea salt, ground black pepper, and ranch seasoning.
Remove from heat then stir in Parmesan cheese, 1 cup of each cheese-mozzarella and cheddar cheese, until melted.
Add the shredded chicken, cooked pasta and bacon and stir to combine.
Transfer to prepared baking dish and top with remaining mozzarella and cheddar. Bake, uncovered, for about 15-20 minutes, until bubbly and cheese is melted.
Garnish with additional bacon and freshly chopped parsley, if desired.