Start by boiling water in a large pot. Add the penne pasta and cook according to the package instructions until al dente. Drain the pasta in a colander and set aside.
In the same pot, heat the olive oil over medium heat. Add the shredded chicken, buffalo sauce, garlic powder, onion powder, salt, and black pepper. Stir well to combine and heat through, about 3-4 minutes.
Reduce the heat to low and pour in the heavy cream and ranch dressing. Stir until smooth and gently simmer for another 2-3 minutes.
Add the cooked pasta to the skillet and toss to coat it thoroughly in the buffalo chicken mixture.
Stir in 1 cup of shredded cheddar cheese until melted and evenly distributed.
If desired, transfer the pasta to a baking dish, top with remaining cheese, and place under the broiler for 2-3 minutes until the cheese is bubbly and slightly golden.
Remove from the oven and let it cool for a few minutes before serving. Garnish with chopped green onions and a drizzle of extra buffalo sauce if desired.