To make the dough, combine the flour and sugar in a bowl. Add the butter and blend until it forms a crumbly consistency. Slowly add 1/2 cup water and mix until it starts to form a dough. Gather it into a ball and place in plastic wrap. Flatten into a disk and refrigerate for at least an hour.
To prepare filling, whisk cornstarch and remaining water in a small saucepan until smooth. Add preserves and heat on medium until it boils. Lower heat and simmer, stirring constantly for about 2 minutes. Remove from heat and let cool.
When the dough is ready, place on a lightly floured work surface and roll into a rectangle about 1/8” thick. Cut into even rectangles about 3” x 4” each. Depending on your work space, you may want to split the dough and work in 2 batches.
Add filling to the center of half the rectangles, leaving 1/4” clean around the edges. Place the uncoated rectangles on top of those with filling and press down on the edges to seal the dough. Using a fork, press around the edges. Then poke holes in the top to let steam escape.
Bake at 400° for 20 minutes or until golden. Let cool.
Prepare icing by combining confectioner’s sugar, water, and vanilla. If too runny, add a bit more sugar. Drizzle on top of the pop tarts as you like. Let dry and serve.
