Instructions:
Preheat the oven to 350°F and line a baking sheet with parchment paper.
Melt the butter in a medium skillet over medium heat. Add the apples, 1/2 cup of the sugar, cinnamon and nutmeg and sauté just until the apples are slightly soft. Remove from the heat and allow to cool.
Once cool, transfer to a large mixing bowl and add the cheddar, mixing until well combined.
Lightly dust a work surface with flour and roll the puff pastry to a 1/4-inch thick 12 x 18-inch rectangle, trimming the edges as necessary. Cut the pastry first in half lengthwise and then cut each half into thirds.
Place 2-3 tablespoons of the apple filling in the center of each puff pastry square. Lightly brush the edges of the pastry squares with egg wash, fold into triangles, and press the edges with the tines of a fork to seal.
Arrange the turnovers on the prepared baking pan and make three 1/2-inch slits on the top of each turnover. Brush the turnovers with the egg wash, and chill in the refrigerator for 30 minutes.
Brush the chilled turnovers again with egg wash, and sprinkle with the sugar. Bake the turnovers until golden brown, about 20minutes, and serve hot with a scoop of vanilla ice cream.