Preheat the oven to 400 F. Lightly grease an 8×10-inch or 2 ½-quart casserole dish with nonstick spray.
Put the cooked chicken in the bottom of the prepared dish. Sprinkle the peas and carrots over the chicken in the baking dish.
In a large saucepan over medium heat melt ¼ cup of the butter. Stir in ¼ cup of flour and cook for 1 minute. Slowly add in the chicken broth and cook until slightly thickened, about 3 minutes. Slowly add in ½ cup of heavy cream. Stir in the onion powder, garlic powder, ½ teaspoon salt, pepper, and cayenne pepper.
Pour the sauce over the chicken and vegetables in the casserole dish. Set aside.
In a large bowl whisk together the remaining 1 cup flour, ¼ teaspoon salt, baking powder, and sugar. Add the remaining ¼ cup butter to the bowl, use a fork or your fingers to cut the butter into the flour mixture until the mixture resembles coarse crumbs. Add the remaining ½ cup heavy cream and mix until the mixture becomes a shaggy dough.
On a lightly floured surface roll out the dough until it is about ½ inch thick, then cut out biscuits with a biscuit cutter or the floured edge of a glass. Place the cut-out biscuits over the chicken and vegetables in the casserole dish.
Bake in the preheated oven for 25 to 30 minutes, until the biscuits are golden brown. Serve hot.