Cast Iron Turkey and Biscuits Casserole

This is comfort food at its best!  I love cooking in cast iron-especially in the fall!  This recipe is really quite easy and absolutely wonderful!

Biscuit Dough:
1-1/2 cups all-purpose flour
2 teaspoons baking powder
1 teaspoon sugar
1/2 teaspoon salt
5 tablespoons cold butter, cubed

1/2 cup plus 2 tablespoons milk, plus milk
to brush on biscuits

Turkey Filling:
2 tablespoons butter
2 tablespoons canola oil
2 medium carrots, peeled and diced
1 large stalk celery, trimmed and diced
1 medium yellow onion, peeled and diced
1 cup frozen pearl onions, defrosted
1/3 cup all-purpose flour
3 cups chicken broth
salt and pepper to taste
2 tablespoons finely chopped flat-leaf parsley
1 tablespoon fresh thyme leaves or 1 teaspoon dried
1 pound cooked turkey, cut into bite-size pieces (about 4 cups)
1 cup frozen peas, defrosted

Prepare the biscuit dough:  Combine the flour, baking powder, sugar and salt in a medium bowl.  Cut in the butter with a pastry blender until mixture resembles coarse crumbs.  Pour in the milk and stir together with a fork until mixture comes together; pat into a ball, flatten into a 3/4-inch-thick disc and dust with flour.  Cover with plastic wrap and refrigerate.  Preheat oven to 450 degrees.  Position rack in middle of oven.  Heat the butter and oil in a deep 10-inch cast-iron Dutch oven over medium-high heat until hot.  Add the carrots, celery, and yellow onion and cook until lightly browned, 5 to 6 minutes.  Add the pearl onions and cook, stirring, until the pearl onions are lightly browned, 5 to 6 minutes more.  Stir in the flour and cook until pale golden color, 1 to 2 minutes.  Pour in the broth, stir until blended, and bring to a boil, stirring constantly; reduce heat and simmer until the sauce thickens, about 3 minutes.  Add the turkey and return the liquid to a boil.  Stir in the peas, parsley, and thyme, season to taste with salt and pepper, and keep warm over low heat.
Finish biscuits:  Lightly dust a work surface with flour.  Roll out or pat the dough into a 1/2-inch-thick disc.  With a 2-1/2-inch cookie cutter, cut the dough into circles, gathering any extra dough together and re-rolling it.  Lay the biscuits over the turkey mixture, carefully brush the tops with milk, and transfer the pot to the oven to bake until the biscuits are golden brown on top, about 23 minutes. Remove and let stand 10 minutes before serving.  Serves 4 to 6  (I doubled this for my family.)
adapted from Cast Iron Cookbook