Preheat the oven to 350°F (175°C). 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 mini muffin cup, gently forming a little cup. Repeat until the pans are filled.
Spoon the buffalo chicken mixture into each wonton cup, filling most of the way but leaving a small rim so the wonton edges can crisp.
Bake for 18–20 minutes, until the filling is bubbly and the wonton edges are golden brown.
Remove from the oven and garnish as desired with extra hot sauce and sliced green onions before serving.