Chicken Biscuit Pie

1/3 cup butter - 1 onion, chopped - 1/3 cup all-purpose flour - 1 & 1/2 cups chicken broth - 2/3 cup milk - 1/2 Tsp salt - 1/4 Tsp ground black pepper - 1 cup frozen green peas - 1 cup frozen diced carrots - 2 cups cooked, shredded chicken meat - 2 cups flour - 2 & 1/2 Tbsp baking powder - 3/4 Tsp salt - 5 Tbsp shortening - 3/4 cup milk

Preheat oven to 450ºF (230ºC). Butter a 2-quart casserole dish.
In a large saucepan, Sauté chopped onion in the butter. Stir in flour and cook for 1 minute. Add chicken broth and milk. Heat to boiling, stirring constantly. Reduce heat to medium and cook and stir for 2 minutes more. Season with salt and pepper. Add frozen peas and carrots and cooked chicken. Pour into prepared casserole dish.
In a medium bowl, mix together 2 cups flour, baking powder, and 3/4 Tsp salt. Cut in shortening until mixture is crumbly. Stir in milk just until dough is moistened, then drop by spoonfuls onto chicken mixture.
Bake at 450ºF (230ºC) for 12 to 15 minutes, or until biscuits are golden brown, and cooked on the bottom. This tends to bubble over so I place a piece of aluminum foil under the pan to catch the drips.