Classic Chicken Pot Pie Recipe

Name: Classic Chicken Pot Pie Recipe
Ingredients: 2 tablespoons olive oil; 1 1/2 pounds boneless chicken thighs, cut into 1-inch chunks; 1 large yellow onion, diced; 2 large carrots, peeled and diced; 2 stalks celery, diced; 1/4 cup unsalted butter; 1/4 cup all-purpose flour; 3 cups chicken stock; 1 tablespoon fresh thyme leaves, stripped off stem; 1/2 cup heavy cream; 1 cup peas, thawed if frozen; 1 cup pearl onions, thawed if frozen; 1 large sheet frozen puff pastry, thawed; 1 large egg, beaten