Preheat the oven to 350°F.
Add melted butter to the bottom of a 9x13-inch baking pan and place the 9x13-inch dish on a large, rimmed baking pan.
½ cup salted butter
Add the shredded chicken to the pan, spreading around to make an even layer over the bottom.
4 lbs shredded chicken breast
Spread the peas and carrots out over the chicken.
12 ounces frozen peas and carrots
Whisk together the cream of chicken soup and the chicken broth in a medium bowl and pour over the ingredients in the pan, don't mix.
1½ cups chicken broth, 1 (10.5 oz) can cream of chicken soup
Whisk together the milk, biscuit mix, and seasoning from the box. Add the cheddar cheese and old bay seasoning if using. Pour the mixture into the dish; again, don't mix.
2 cups whole milk, 1 (11.36 oz) box Red Lobtser Cheddar Biscuits mix, 1 cup shredded cheddar cheese, 1 tablespoon old bay seasoning (or seasoning of choice)
Bake for 50 to 60 minutes.