Puff Pastry Apple Turnovers with Brown Butter

Description

1. Preheat oven to 425°F. Line a large rimmed baking sheet with parchment paper.
2. Combine apples, brown sugar, cinnamon and salt in a medium bowl; toss until fully coated.
3. Cook butter in a large skillet over medium heat, stirring occasionally, until the butter solids are amber in color and nutty in aroma, 3 to 5 minutes. Add the apple mixture; cook, stirring occasionally, until the apples are softened and caramelized, 7 to 8 minutes.
4. Whisk cider vinegar and cornstarch together in a small bowl to create a slurry. Reduce heat to low; add the cider vinegar mixture to the pan and cook, stirring constantly, until the pan is dry and the apples are glazed, 1 to 2 minutes. Transfer the mixture to a plate; refrigerate, uncovered, until completely cool, about 30 minutes.
5. Unfold puff pastry sheets onto a work surface. Cut each sheet into 4 squares. Cut each square in half diagonally to create a total of 16 triangles. Transfer 8 triangles to the prepared baking sheet, spacing them 1 inch apart.
6. Scoop about 2 tablespoons apple filling into the center of each of the 8 triangles on the baking sheet, leaving about a 1/4-inch border on all sides of the triangle.
7. Whisk egg and milk together in a small bowl until fully combined. Using a pastry brush, brush the edges of the triangles with the egg mixture. Carefully place the remaining triangles on top of the filling, aligning the edges. Brush the tops with egg mixture; use a fork to crimp and seal the edges.
8. Bake until puffed and deep golden brown, 18 to 20 minutes. Let cool on the pan for 5 minutes; serve warm.