Chicken Piccata Potpie

Ingredients

• 1/2 (17.3-ounce) package frozen puff pastry sheets, thawed
• 1/4 cup unsalted butter
• 1 shallot, sliced into rings (about 1/4 cup)
• 6 garlic cloves, thinly sliced (about 3 tablespoons)
• 1/2 cup dry white wine
• 1/2 cup all-purpose flour (about 2 1/8 ounces), plus more for work surface
• 2 1/2 cups chicken broth
• 4 cups shredded rotisserie chicken (about 1 pound)
• 1/4 cup fresh lemon juice (from 2 medium lemons)
• 1/4 cup drained nonpareil capers
• 1/4 cup chopped fresh flat-leaf parsley, plus more for garnish
• 1/2 teaspoon plus 1/8 kosher salt, divided
• 1/4 teaspoon plus 1/8 teaspoon black pepper, divided
• 1 large egg
• 1 tablespoon tap water

Steps

1. Preheat oven to 400°F with rack in lower third position. On a lightly floured surface, roll puff pastry into a 10-inch square. Cut 2 to 3 (2-inch) slits horizontally across the center of pastry, spacing each 1-inch apart. Place on a large plate or small baking sheet, chill while you build the filling.
2. Melt butter in a deep 10-inch ovenproof skillet over medium. Add shallots and garlic; cook, stirring often, until softened, about 2 minutes. Stir in wine and bring to a boil over medium; cook until reduced by half, about 2 minutes, stirring occasionally. Whisk together flour and chicken broth in a measuring cup; stir into skillet and cook, whisking constantly, until mixture thickens, 1 to 2 minutes. Stir in chicken, lemon juice, capers, parsley, 1/2 teaspoon salt, and 1/4 teaspoon pepper. Remove from heat.
3. Whisk together egg and water in a small bowl. Place pastry square over hot chicken mixture, letting ends extend over sides of skillet. Brush pastry evenly with egg wash. Sprinkle with remaining 1/8 teaspoon each salt and pepper. Brush the undersides of the puff pastry corners with the egg wash; press to the skillet. Place skillet on a rimmed baking sheet.
4. Bake until top is browned and filling is bubbly, about 20 minutes. Remove from oven and let stand 10 minutes. Sprinkle with fresh parsley and serve.