Chicken Pot Hand Pies

Name: Chicken Pot Hand Pies
Ingredients: 4 cups (1 liter) low-sodium chicken broth; One 8-ounce chicken breast; 2 tablespoons unsalted butter; 1 leek or yellow onion, diced; 1 stalk celery, diced; 1 carrot, peeled and diced; Kosher salt and freshly ground black pepper; 1 garlic clove, minced; 2 tablespoons all-purpose flour; 1/2 cup (125 milliliters) frozen peas; 2 tablespoons finely chopped parsley; 1/4 cup (20 grams) grated Parmigiano-Reggiano; 2 tablespoons sour cream; One 14- to 16-ounce (400- to 450-gram) package frozen puff pastry, thawed according to package directions; 1 large egg; 1 tablespoon milk or water