📋 Instructions

1. 1Grate and chill the butter — Grate the frozen butter on the large holes of a box grater onto a plate and return it to the freezer for 10 minutes. Cold shreds are what create those flaky layers.
2. 2Make the dough — Whisk the flour, granulated sugar, and salt in a large bowl, toss in the grated butter until coated, then drizzle in 6 tablespoons of ice water and squeeze the dough into a shaggy ball, adding water a tablespoon at a time until it just holds. Flatten into two discs, wrap, and chill for 30 minutes.
3. 3Mix the filling — Stir the brown sugar, cinnamon, and flour together in a small bowl until no lumps remain. Set aside while the dough chills.
4. 4Roll and cut rectangles — Roll each disc on a floured surface to 1/8-inch (3mm) thickness and cut into 12 rectangles about 3 by 4 inches, re-rolling scraps once. You should have 24 rectangles for 12 tarts.
5. 5Fill and seal — Brush the border of 12 rectangles with egg wash, spoon 2 level tablespoons of filling into the center, top with a second rectangle, and press the edges shut with a fork. Crimp twice for a tight seal.
6. 6Chill before baking — Transfer the tarts to a parchment-lined baking sheet and freeze for 10 minutes while the oven heats to 375°F (190°C). Chilled pastry holds its shape and puffs properly.
7. 7Bake until golden — Prick each top three times with a fork and bake at 375°F (190°C) for 22 to 25 minutes, until the edges are deep golden brown and the filling bubbles faintly at the seams. Let cool on the pan for 10 minutes, then move to a rack.
8. 8Frost and set — Whisk the powdered sugar, milk, vanilla, and maple extract into a thick, pourable icing, spread about 1 tablespoon over each barely warm tart, and let it set for 20 minutes before serving.