Chicken Pot Pie Turnovers

INGREDIENTS

• 2 tablespoons butter
• Kosher salt and freshly ground black pepper
• 1 egg
• 2 teaspoons dried thyme
• 1/2 onion, chopped
• 1 1/2 cups cubed or shredded cooked chicken
• 1 stalk celery, chopped
• 1 tablespoon flour, plus more for dusting
• 1 sheet frozen puff pastry, thawed
• 1/2 cup white wine
• 1 cup chicken stock
• 2 cloves garlic, minced
• 1/2 cup frozen peas
• 1 carrot, chopped
• 1 teaspoon Dijon mustard