**This recipe is by Claire Saffitz: https://www.bonappetit.com/story/claire-saffitz-gourmet-pop-tarts
How to:
Pastry Dough
Whisk flour, sugar, and salt in a large bowl to combine. Add it to a food processor together with the cold butter. Process until the largest pieces are about the size of a lentil.
Then drizzle water into the mixture (one tbsp at a time) around 1 dl. Until it turns into a dough. Remove from the processor and knead it by hand until it turns smooth.
Transfer dough to a sheet of plastic wrap and pat into a 1cm-thick square. Wrap tightly, pressing out air, then roll over dough with a rolling pin in both directions, forcing it into the corners of the wrapping to make a tightly compacted square. Chill at least 2 hours but preferably overnight.
Filling
Preheat the oven to 120°. Combine strawberries, granulated sugar, salt, and water in a large saucepan and cover. Bring to a simmer over medium heat, uncovering and stirring occasionally, until berries are softened, about 5–8 minutes.
Remove from heat and purée with a hand blender, leaving a bit of texture if you like. Return to a simmer, uncovered, and cook, stirring often with a heatproof rubber spatula, being sure to scrape the sides and bottom of pan, until the filling is thick enough that you can see the bottom of the pot for a second when you scrape the spatula across, 10-15 minutes.
Scrape filling onto a large baking sheet lined with a silicone mat and spread into a thin, even layer. Bake, stirring every 15 minutes with spatula, until it becomes a thick paste that holds its shape (it should resemble tomato paste), 45–60 minutes. Let cool, then transfer filling to a small bowl and stir in vanilla. Add lemon zest and juice to taste.
Assembly
Preheat the oven to 150C°. Unwrap dough and cut in half. Re-wrap one half and return to the refrigerator. Roll out remaining dough on a lightly floured surface to about 35.5cm x 25.5cm rectangle. Transfer to a baking sheet lined with parchment paper.
Using a ruler, lightly score straight lines on dough to make a 3x3 grid (you should have 9 rectangles each measuring about 11cm long and 8cm wide (don’t cut all the way through the pastry). Using the ruler, measure and lightly score another set of lines 0.5cm from the inside of each rectangle (think of it as making a slightly smaller rectangle inside each of the 9 rectangles. Chill dough until firm, 10–15 minutes.
Remove scored dough from the refrigerator and divide cooled filling among rectangles (about a slightly heaping tablespoonful each). Using a small offset spatula or a spoon, spread filling in an even layer so it fills up to the lines of the smaller rectangles (you’re leaving the 0.5 cm border exposed). Transfer to the refrigerator to chill. Roll out the second piece of pastry into a 11cm x 8cm rectangle the same way as the first, then prick it all over with a fork.
Seperate the egg, letting the egg white fall into a medium bowl (for making the icing later). Place egg yolk in a small bowl and blend. Remove pastry with filling from the refrigerator and brush egg yolk over pastry, working around the filling. Drape the second piece of pastry over top, aligning the slabs and pressing out any air pockets. Press firmly around the filling to seal pastry (take care to avoid the filling though). Use a bench scraper to cut down between rectangles to make nine 11cm x 8cm pop tarts; discard any scraps. Space pop tarts evenly on the baking sheet. Chill until the pastry is firm, 10–15 minutes.
Bake pop tarts until golden underneath and puffed but still pale on top, 30–35 minutes. Let cool on the baking sheet.
Add salt to reserved egg white and whisk until foamy. Add powdered sugar a little bit at a time, whisking constantly and vigorously until you have a smooth, opaque white icing that falls off the whisk in a slowly dissolving ribbon (depending on the size of your egg white, you might not need all the sugar). Fill a disposable pastry bag or a resealable plastic bag with about 2 Tbsp. icing and snip a very small opening from the end or a bottom corner. Pipe thin, even rectangles of icing on the surface of each pop tart, leaving about 0.5cm border.
Transfer any icing left in the bag back to the bowl, then whisk in lemon juice and vanilla. Whisk in water a few drops at a time if needed to make the icing a bit more fluid but still thick and opaque. Working with 1 pop tart at a time, drizzle about 1 tsp. icing inside the icing rectangles and use your finger or a toothpick to cover the entire icing rectangle in a thin, even layer (add more icing if needed). You should have a smooth, even application of white icing. Before the icing starts to set, top pop tarts generously with sprinkles. Let sit at room temperature at least 1 hour to let the icing set before serving.
