Dutch Letters

In a large bowl, whisk together flour and salt; add butter and toss until flour evenly coats butter. In a small bowl, mix 1 egg with 1 cup cold water and add to flour-butter mixture; stir to form a loose dough. Transfer dough to a floured work surface, and knead until dough comes together, about 10 strokes. Roll dough into a 15" x 10" rectangle. Fold up the 2 short sides of rectangle so they meet in middle, and then fold dough like a book. Rotate rectangle 90°; repeat rolling and folding technique. Wrap dough in plastic wrap and chill for 20 minutes. Uncover; and repeat rolling and folding technique twice more. Wrap dough with plastic wrap and chill 1 hour.

Meanwhile, in a medium bowl, beat almond paste and 1 egg white on medium-high speed of a hand mixer until smooth. Add remaining egg white and the sugars, and beat until smooth, 1-2 minutes; set filling aside. In a small bowl, whisk together remaining egg and milk; set egg wash aside.

Cut dough crosswise into 4 equal pieces. Transfer 1 dough piece to a lightly floured work surface, chilling remaining 3 pieces. Roll dough into a 12 1⁄2" x 10" rectangle; cut rectangle into five 10" x 2 1⁄2" strips. Working with one strip at a time, put 1 heaping tbsp. filling lengthwise down the center of the strip, using your fingers to spread it to each end. Using a pastry brush, brush egg wash down one edge and then, beginning with the dry side, roll strip over filling and into a cigar shape. Transfer pastry rolls, seam side down, to a parchment paper-lined baking sheet and form into an "S" shape; repeat with remaining dough, filling. and egg wash.

Heat oven to 375°. Brush each pastry with egg wash and sprinkle liberally with sugar. Bake, rotating baking sheets once halfway through cooking, until golden brown, 30-35 minutes. Transfer to a rack and let cool for 20 minutes before serving.