Preheat oven to 350°F (175°C).
Pour melted butter into a 9x13-inch baking dish and swirl to coat bottom.
Add shredded chicken in an even layer.
Sprinkle in frozen peas, if using.
In a bowl, whisk together baking mix and milk until smooth. Pour evenly over the chicken. Do not stir.
In another bowl, mix cream of chicken soup and chicken broth until combined. Pour over the batter layer. Do not stir.
Bake uncovered for 45–50 minutes, or until the top is golden brown and edges are bubbling.
Let rest for 10 minutes before serving.