Dice potatoes and cook until tender. Drain well.

In a large bowl, combine cooked chicken, frozen vegetables, and cooked potatoes.

In a medium bowl, mix cream of chicken soup, chopped onion, parsley, and parmesan cheese.

Gently add the soup mixture to the chicken and vegetable mixture and combine.

Transfer the combined mixture to a 9x13 inch baking dish.

Sprinkle cheddar cheese evenly over the top of the casserole.

In a separate bowl, whisk together Bisquick and enough milk to form a thin batter similar to pancake batter.

Pour the Bisquick mixture evenly over the casserole.

Sprinkle paprika over the top for color.

Bake uncovered at 350 degrees Fahrenheit (175 degrees Celsius) for 45 minutes, or until the top is golden brown and bubbly.