In a saucepan bring broth to a boil. Add carrots, potatoes, and
celery, and simmer for 10-15 minutes, or until veggies are tender.
Transfer veggies to a bowl, reserving the broth, and add the chicken
to the bowl. In another saucepan, cook the onion in the butter
over mod-low heat, stirring, until it is softened. Add flour and
cook the roux, stirring, for 3 minutes. Add 3 cups of broth in
a stream, whisking. Bring mixture to a boil, whisking. Add the
thyme and simmer the sauce, stirring occasionally, for 5 minutes.
Stir in nutmeg, parsley, and salt and pepper to taste. Pour the
sauce over the chicken and veggies. Stir the mixture gently, until
it is just combined. Transfer the mixture to a 2-qt. baking dish.
Into a bowl, sift together the flour, baking powder, baking soda,
and salt. Add the butter and shortening and blend the mixture
until it resembles meal. Add the cheese and toss. Break egg into
a measuring cup and add buttermilk to it so that the total volume
is 1/2 cup. Beat with a fork. Add to the flour mixture, stirring
until the mixture just forms dough. Gather dough into a ball and,
on a floured surface, pat it out 1/2-inch thick. Cut as many rounds
as possible using a 2-inch fluted biscuit cutter, dipped in flour.
Gather the scraps and pat and cut again.
Arrange the rounds on the chicken mixture. Beat the egg yolk with
the milk and brush the tops of the biscuits with the wash. Prick
biscuits with a fork.
Serves 4.
Bake in the middle of a preheated 450f oven for 15-25 minutes,
or until biscuits are puffed and golden, and the filling is bubbling.
a 1985 Gourmet Magazine favorite, as posted to a cooking forum.