Preheat and prep: Preheat oven to 375°F. Lightly grease a 9x13-inch baking dish and set aside.
Fill crescents: Unroll crescent dough and separate into triangles. Place about 2 tablespoons cooked chicken and small amount of cheddar cheese at wide end of each triangle. Roll up starting at wide end toward point, enclosing filling. Place seam side down in prepared dish.
Make sauce: In medium bowl, whisk together cream of chicken soup, milk, garlic powder, onion powder, and black pepper until smooth.
Assemble: Pour sauce mixture evenly over crescent rolls in baking dish, spreading into gaps. Sprinkle remaining cheese over top.
Bake: Bake for 25-30 minutes until crescents are golden brown and sauce is bubbling. Cheese should be melted and lightly browned.
Rest and serve: Remove from oven and let rest 5 minutes before serving. Garnish with parsley if desired.