HOMEMADE STRAWBERRY-RHUBARB TOASTER TARTS

Steps:

• For the dough: Pulse the flour, granulated sugar and salt in a food processor until combined. Add the butter and pulse until the mixture looks crumbly. Drizzle in the beaten egg and pulse until the dough holds together when pinched. Add 3 to 4 tablespoons cold water and pulse until the dough just comes together. Turn out onto a clean surface and knead a few times until the dough comes together. Divide the dough into 2 mounds then roll out each mound between two sheets of parchment into a 12-inch round (about 1/8 inch thick). Wrap each round in plastic then refrigerate until firm, about 1 hour.
• Meanwhile, make the cheese Danish filling: Beat the cream cheese and the granulated sugar with an electric mixer on medium-low speed in a medium bowl until smooth. Add the lemon zest, vanilla and salt, and mix on low speed until just combined. Set aside at room temperature until ready to assemble.
• Position the racks in the upper and lower thirds of the oven and preheat to 400 degrees F. Line 2 rimmed baking sheets with parchment.
• Cut 1 round of the chilled dough into nine 3-by-4-inch rectangles. Transfer to the prepared baking sheets, leaving about 1 1/2 inches between each piece (these are the bottom crusts). Repeat the cutting with the second round of dough and set these 9 rectangles aside (these are the top crusts). Discard any scraps of dough.
• For the rhubarb filling: Toss the rhubarb and strawberry jam together in a medium bowl until combined, then divide among the bottom crusts. Do your best to spread the rhubarb mixture into an even layer, leaving a 1/4-inch border around the edges.
• Top the rhubarb filling with the cheese Danish filling (about 2 tablespoons on each bottom crust), smoothing into an even layer with a small offset spatula. Cover each bottom crust with a top crust and crimp the edges together with a fork. Freeze the tarts on the baking sheets until chilled through, about 30 minutes.
• For the egg wash: Whisk the egg with 1 teaspoon water in a small bowl until combined, then brush on the top of each tart.
• Bake the tarts until the crust has puffed and turned golden brown, rotating the baking sheets halfway through, 20 to 25 minutes. Transfer to wire racks to cool completely.
• For the icing and sprinkles: Whisk the confectioners' sugar and milk together in a small bowl until smooth and spreadable. Spoon the icing over each tart then sprinkle with the nonpareils as you go so they adhere before the icing sets. Let the icing set before serving, about 10 minutes.