Chicken Pot Shepherd's Pie | Saveur

Ingredients

• 3 lb. russet potatoes, peeled and cut into 1-inch pieces
• Kosher salt and freshly ground black pepper
• 4 1⁄2 cups milk
• 14 tbsp. unsalted butter
• 2 lb. chicken breast, cut into 1-inch pieces
• 10 oz. button mushrooms, quartered
• 1⁄2 medium yellow onion, finely chopped
• 1 red bell pepper, stemmed, seeded, and finely chopped
• 1⁄2 cup flour
• 1 cup fresh or frozen peas
• 2 sheets puff pastry
• 1 egg, lightly beaten