Name: Blueberry Turnovers (Reduced Sugar)
Total time: 1 h 15 min
Ingredients: 1¼ pounds (567 grams/4 cups) blueberries; ¼ cup maple syrup; ½ teaspoon grated lemon zest plus 1 tablespoon juice; ⅛ teaspoon salt; Pinch ground cinnamon; 1 tablespoon cornstarch; 1 tablespoon water; 2 (9½ by 9-inch) sheets puff pastry , thawed; 1 large egg white , lightly beaten

Why This Recipe Works

We knew that the blueberries needed to be cooked to drive off any excess moisture before we filled our pastries. For our first test, we made a filling without any sweetener and just a touch of lemon juice, since the acid would help to activate the natural pectin in the berries and encourage the filling to thicken. But tasters found this filling a bit too runny, and they wanted more sweetness and complexity. We decided to sweeten the filling with maple syrup, which tasters preferred over honey—the maple's subtler flavor didn't interfere with the brightness of the blueberry filling. Reserving some extra syrup to brush on the tops of the turnovers provided extra sweetness and encouraged browning. To fix the filling's texture, we tried cooking the filling down until it resembled jam, but the longer cooking time eliminated much of the fresh berry flavor, and the blueberries tasted a bit flat. We decided instead to add some cornstarch to the blueberries toward the end of cooking; this reduced the overall cooking time and preserved the subtle flavors of the blueberries. Freezing the turnovers briefly before baking ensured that the puff pastry baked into perfectly flaky layers. Finally, our turnovers were packed with intense blueberry flavor and the filling had the perfect consistency.

Before You Begin

To thaw frozen puff pastry, let it sit in the refrigerator for 24 hours or on the counter for 30 minutes to 1 hour; do not microwave the pastry.

Instructions

Adjust oven rack to middle position and heat oven to 400 degrees. Line rimmed baking sheet with parchment paper. Combine blueberries, 2 tablespoons maple syrup, lemon zest and juice, salt, and cinnamon in medium saucepan. Cook over medium heat, stirring occasionally, until blueberries begin to break down, release their juices, and mixture begins to thicken, 18 to 20 minutes.

Whisk cornstarch and water together in bowl, then add to blueberries and cook until mixture has thickened to jam-like consistency, about 1 minute. Remove from heat and let cool to room temperature, about 20 minutes.

On lightly floured counter, roll each pastry sheet into 10-inch square, then cut each into four 5-inch squares, for a total of 8 squares. Place 2 tablespoons blueberry mixture in center of each square. Brush edges of dough with 1 teaspoon of remaining maple syrup, then fold dough over filling to form rectangle. Crimp edges with fork to seal.

Using paring knife, cut two ½-inch slits in tops of turnovers. Transfer turnovers to prepared sheet and brush with remaining 5 teaspoons maple syrup. Freeze turnovers until firm, about 20 minutes. (Once frozen, turnovers can be transferred to airtight container and frozen for up to 1 month)

Brush frozen turnovers with beaten egg white and bake until well browned, 20 to 26 minutes, rotating sheet halfway through baking. Transfer turnovers to wire rack and let cool slightly, about 20 minutes. Serve warm or at room temperature.