5 tablespoons unsalted butter
1 sheet puff pastry (half of 17.3-ounce package), thawed
1 medium onion, coarsely chopped
3 ribs celery, diced
2 cloves garlic, crushed
3 carrots, coarsely chopped
4 tablespoons flour
1 cup dry white wine
2 cups chicken broth
Kosher salt, ground pepper
4 sprigs fresh thyme
1 cup frozen green peas, thawed
1 cup frozen pearl onions, thawed
2½ cups cremini mushrooms, trimmed and cut into quarters
¾ cup plus 1 tablespoon heavy cream
1 roasted chicken, skinned, boned and meat shredded
Heat oven to 400 degrees. Grease an 11-by-7-inch baking dish with 1 tablespoon butter. Roll pastry sheet on a lightly floured surface until about 13 by 9 inches. Transfer to a baking sheet; refrigerate at least 30 minutes (and up to three hours).
Melt remaining butter in a large saucepan over medium heat. Add onion, celery, garlic and carrots; cook, stirring occasionally, until softened, about five minutes. Add flour; cook, stirring, two minutes. Add wine and broth and then season generously with salt and pepper. Stir briskly to prevent any lumps forming.
Bring to a boil. Add thyme, peas, pearl onions and mushrooms; reduce heat. Simmer, stirring occasionally, five to eight minutes. Stir in ¾ cup cream and chicken; remove from heat. Pour mixture into baking dish.
Remove pastry from the refrigerator and working quickly, place the dough over the top of the chicken mixture, and tuck extra dough around the edges. Cut slits on top to allow steam to escape. Brush with remaining cream and place on a baking sheet. Bake until crust is golden, 35 to 40 minutes. Serve hot.
Per serving: 464 calories; 17.3 grams protein; 26.7 grams carbohydrates; 30.3 grams fat (13.8 saturated, 11.7 monounsaturated); 84.7 milligrams cholesterol; 408 milligrams sodium; 3 grams fiber; 58 percent calories from fat.