Chicken and Sweet Potato Pot Pies

Heat oven to 375 degrees F. Oil four 12-ounce ramekins (each about 4-inch round) or a 9-inch pie plate. Heat oil in a large skillet over medium heat. Add onion, 1/2 teaspoon each salt and pepper, and cook, covered, stirring occasionally, for 6 minutes. Add sweet potatoes and cook, covered, stirring occasionally until tender, 8 to 10 minutes. Meanwhile, shred chicken, discarding skin and bones; set aside. Sprinkle flour over the vegetables and cook, stirring, for 1 minute. Gradually stir in wine and then broth and bring to a boil. Add chicken, peas, parsley, tarragon (if using), and nutmeg. Divide mixture among prepared ramekins (about 3/4 cup each). Place ramekins on a rimmed baking sheet. Using a 4-inch round cookie cutter, cut out 4 pieces of puff pastry (or cut out one large circle). Place pastry on top of ramekins (or pie plate). Place pot pies on a rimmed baking sheet. Brush pastry with egg and if desired, using a sharp knife, cut three slits in top of each piece of pastry. Bake until puffed and golden brown, 20 to 25 minutes.