For pastry lids: Thaw pastry according to package directions. Line a large baking sheet with parchment paper or foil; set aside. On a lightly floured surface, roll each puff pastry sheet to a 14-inch square. Using 10-ounce individual ramekins as a guide, turn upside down on pastry. Cut out 8 rounds from the dough using a sharp knife.
Using a fork, prick holes over each pastry round. Transfer pastry rounds to prepared baking sheet. If you like, use tiny cookie cutters to make cutouts from remaining pieces of puff pastry. Brush cutouts lightly with water and press gently to adhere 1 to 3 cutouts to each of the pastry rounds. Bake in a 400 degree F oven about 12 minutes or until golden brown.
For filling: Lightly coat a Dutch oven with nonstick cooking spray. In the Dutch oven, cook chicken over medium heat until lightly browned and no pink remains, stirring occasionally. Add onion, celery, carrots and garlic; cover and cook over medium heat for 5 to 7 minutes or until tender, stirring occasionally. Stir in flour. Cook and stir 3 minutes.
Add half-and-half. Cook and stir until combined. Add chicken broth and bay leaf. Cook and stir over medium heat until thickened and bubbly; cook and stir for 1 minute more. Season to taste with salt and pepper. Stir in peas. Remove pan from heat. Remove bay leaf; discard.
To serve, spoon hot chicken mixture into eight 10-ounce individual ramekins or casserole dishes and place a puff pastry lid on top of each. Serve immediately.