Foryoueats: Turkey and Dumplings

Ingredients

• 6 tablespoons unsalted butter
• 3 tablespoons plus 1 1/2 cups all-purpose flour, divided
• 1 1/2 quarts (48 ounces) homemade or store-bought low sodium chicken broth
• 1 cup leftover gravy (optional)
• 1 large onion, finely sliced (about 1 1/2 cups)
• 2 medium carrots, chopped medium (about 1 1/2 cups)
• 3 medium ribs celery, chopped medium (about 1 1/2 cups)
• 1 pound leftover roast turkey, torn into rough bite-sized pieces (see note)
• 1 1/2 cups thawed frozen peas
• 1/2 cup minced fresh parsley leaves
• Kosher salt and freshly ground black pepper
• 1/2 teaspoon baking powder
• 2 tablespoons minced fresh chives
• 1/2 cup buttermilk
• 1 whole egg