Cook penne according to package instructions until al dente. Drain and set aside.

In a large skillet, heat olive oil over medium heat. Add the diced onion and minced garlic, sautéing until translucent. Add the cooked, shredded chicken and buffalo wing sauce, stirring to combine. Cook for 5 minutes, then remove from heat.

In a large mixing bowl, combine the cooked penne, buffalo chicken mixture, ranch dressing, milk, half of the mozzarella cheese, and salt and pepper. Mix well.

Transfer the pasta and chicken mixture to the prepared baking dish. Top with the remaining mozzarella and blue cheese crumbles.

In a small bowl, mix together panko breadcrumbs and grated Parmesan cheese. Sprinkle evenly over the top of the casserole.

Place the casserole in the preheated oven and bake for 25-30 minutes, or until the topping is golden brown and the casserole is bubbling.

Garnish with additional crumbled blue cheese and chopped fresh parsley. Let cool for a few minutes before serving.