Preheat oven to 400°F. On a lightly floured surface, roll each pastry sheet to a 10-inch square; cut each into four 5-inch squares. Set aside.
Lightly coat a Dutch oven with cooking spray; heat Dutch oven over medium heat. Add chicken; cook until light brown, stirring occasionally. Stir in onion, celery, carrots, and garlic. Cook, covered, over medium heat for 5 to 7 minutes or until vegetables are tender, stirring occasionally.
Stir flour into chicken mixture; cook and stir for 3 minutes. Gradually stir in half-and-half until combined. Add broth, bay leaf, salt, and pepper. Cook and stir over medium heat until thickened and bubbly. Cook and stir for 1 minute more. Stir in frozen peas. Remove from heat. Remove and discard bay leaf.
Spoon hot chicken mixture into eight 10-ounce individual ramekins or baking dishes. Top with pastry squares. Bake for 10 to 12 minutes or until pastry is golden.