Preheat oven to 350°F. Spray 16 wells of two 12 cup muffin pans with cooking spray.
Unroll crescent rolls and separate at perforations into 16 triangles. Press one piece into each cup of prepared muffins pans leaving 3 pointed edges free. 16 total.
In a mixing bowl using an electric mixer, whip together cream cheese, mayonnaise and dry ranch dressing mix for 2 minutes until fully combined.
Mix in chicken, cheese, bacon and green onion by hand.
Divide filling evenly among crescent rolls. Bring pointed edges together and pinch to close.
Brush the tops with butter and sprinkle with Parmesan cheese.
Bake for 18-20 minutes or until golden. Cool in pan 2 minutes, then remove to platter and serve.