In a small bowl, combine flour and salt; cut in 1/4 cup butter until crumbly. Gradually add water, tossing with a fork until a ball forms. On a lightly floured surface, roll dough into a 12x6-in. rectangle., Cut remaining butter into thin slices. Starting at a short side of dough, arrange half of the butter slices over two-thirds of rectangle to within 1/2 in. of edges. Fold unbuttered third of dough over middle third. Fold remaining third over the middle, forming a 6x4-in. rectangle. Roll dough into a 12x6-in. rectangle., Repeat steps of butter layering and dough folding, ending with a 6x4-in. rectangle. Wrap in plastic; refrigerate for 15 minutes. Roll dough into a 12x6-in. rectangle. Fold in half lengthwise and then widthwise. Wrap in plastic; refrigerate for 1 hour., Preheat oven to 450°. Meanwhile, in a small saucepan, combine the sugar, cornstarch and cinnamon. Add apples and lemon juice; toss to coat. Bring to a boil over medium heat, stirring constantly. Reduce heat; simmer, uncovered, until apples are tender, stirring often, 5-10 minutes. Remove from the heat., In a small bowl, combine egg and water. Roll dough into a 12-in. square; cut into four squares. Brush with half of the egg mixture. Spoon about 1/4 cup filling on half of each square; fold dough over filling. Press edges with a fork to seal. Place on an ungreased baking sheet. Brush with remaining egg mixture. With a sharp knife, cut three small slits in the top of each turnover., Bake until golden brown, 17-22 minutes. Remove to a wire rack. Combine glaze ingredients; drizzle over turnovers. Serve warm.