Preheat the oven to 350°F (175°C) and spray two mini muffin pans with nonstick cooking spray.
In a large mixing bowl, combine the chopped cooked chicken, softened cream cheese, ranch dressing, Frank's hot sauce, garlic powder, onion powder, and shredded cheddar until evenly mixed and creamy.
Press one wonton wrapper into each greased mini muffin cup, gently pressing to form a cup shape.
Spoon the buffalo chicken mixture into each wonton cup, filling most of the way but leaving a small rim so filling does not overflow.
Bake the filled wontons for 18–20 minutes, until the filling is bubbly and the wonton wrappers are golden brown.
Remove from the oven and garnish as desired with extra hot sauce and sliced green onions before serving.