With a buttery, flaky crust, fresh sweet jam, and perfectly sticky frosting, homemade pop tarts are worth the extra effort. They make a wonderfully decadent breakfast in the morning or a crowd-pleasing dessert in the evening.
In the bowl of a food processor, combine all-purpose flour, granulated sugar and coarse salt and pulse until combined. Add butter and pulse until the mixture is the texture of coarse meal with some larger pea-sized pieces of butter. Add 6 tablespoons of the of ice water to the mixture and pulse just until the dough is evenly moistened. You should be able to squeeze a bit of the dough together and have it hold. Add up to two more tablespoons of water if necessary, but don’t let the dough get too wet. Divided the dough in half onto two pieces of plastic wrap. Shape each half into a square, wrap well and chill for at least 2 hours.
On a lightly floured surface, roll the dough into a 8 1/2-inch-by- 12 1/2 inch rectangle. Trim 1/4 inch off each edge then cut the dough into 8 rectangles. Transfer the rectangles to a baking sheet and repeat with the remaining disc of dough.
Preheat the oven to 375°F Make an egg wash by beating 1 egg well. Brush the edges of half of the rectangles with the egg wash. Add 1 tablespoon of the jam to each of those rectangles and spread it out leaving a 1/2-inch border. Top each of these rectangles with another and use a fork to seal the edges. Cut three small slits in the top of each tart to vent steam.
Transfer the tarts to two parchment-lined baking sheets and brush them with egg wash. Bake until deep golden brow, 20 to 24 minutes. Transfer them to a rack to cool completely.
Meanwhile, prepare the frosting. In a medium bowl, whisk together powdered sugar, milk, and vanilla extract. Add a bit more milk for a thinner glaze, if you like. Use a spoon to spread a bit of glaze on the top of each tart. Sprinkle with sanding sugar and serve immediately or let the tarts stand at room temperature until the glaze has set, about 2 hours.