Chicken Pot Pie

Bahan-bahan (4 porsi)

• 1 to 2 packages frozen puff pastry, (best quality such as Dufour or Pepperidge Farm, thawed (see note))
• 4 tablespoons unsalted butter
• 1 medium yellow onion, (diced)
• 3 cloves garlic, (roughly chopped)
• 3 stalks celery, (diced)
• 1 cup frozen pearl onions ((no need to defrost))
• 3 carrots, (sliced into ¼-in (6-mm) rounds)
• 1/3 cup all-purpose flour, (plus more for rolling the pastry)
• 2½ cups low-sodium chicken broth
• ¼ cup Cognac or brandy ((okay to replace with more chicken broth if avoiding alcohol))
• ¾ teaspoon salt
• ½ teaspoon white pepper
• ½ cup heavy cream
• 1 tablespoon chopped fresh thyme ((or a combination of thyme, rosemary and sage), plus a few thyme sprigs for serving)
• 3 to 4 cups shredded cooked chicken, (from 1 rotisserie chicken)
• 1 cup frozen peas ((no need to defrost))
• 1 egg