In a medium saucepan, soften the butter over medium warmth. Add the apple and prepare dinner for 3 minutes, stirring often. Add the sugar, cinnamon, allspice, nutmeg, and salt. Proceed to prepare dinner, stirring typically, till the apples are softened and caramelized. Let cool to room temperature earlier than continuing with the recipe (switch to a bowl and place within the fridge to hurry this course of alongside).
Line a big baking sheet with parchment paper. Take away the primary sheet of puff pastry from the fridge. On a evenly floured work floor, roll it into an 11-inch sq.. With a pointy knife or pizza cutter, slice it into quarters so you might have 4 equal squares.
Scoop one-eighth of the apple filling onto one diagonal half of every sq. (place it in one of many 4 corners of every sq. and go away the opposite half uncovered), leaving a 1/2-inch border on the edges. Brush egg wash evenly on the pastry edges which might be nearest to the apples, then fold the uncovered facet over the apples, making a triangle packet. With the tines of a fork, press the 2 edges the place the pastries meat collectively to seal. Switch to the ready baking sheet, leaving 1 inch between every. Repeat with the remaining filling and puff pastry. Switch to the fridge whereas the oven preheats (or ideally for 20 minutes; refrigerating reduces the chance of the filling leaking out). Maintain the eggwash useful.
Place a rack within the middle of your oven and preheat to 400°F. Brush the highest of every pastry with eggwash, then with a pointy knife, minimize two small vents within the high of every to permit steam to flee. Bake the apple turnovers till the pastry is puffed and golden, about 20 to 22 minutes.
Whereas the turnovers bake, put together the glaze: in a medium bowl, stir collectively the powdered sugar, milk, and vanilla extract. Regulate the consistency as wanted by including extra powdered sugar 1 tablespoon at a time (for a thicker glaze) or extra milk 1 teaspoon at a time (for thinner). The glaze needs to be thick however simple to drizzle. Drizzle over the nice and cozy turnovers. Let cool a couple of minutes, then serve.
