Combine the cold butter, flour, salt and sugar in a food processor. Pulse in short bursts with a couple of seconds breaks between each burst. The key is to keep the butter cold, long bursts will create heat by friction and melt the butter. Once lightly combined add the vodka and pulse 2-3 more times. Last add the ice cold water. Careful don't add too much, go one table spoon at a time. The texture should stay crumbly and NOT become a batter or dough.
Place the crumbly dough on your working surface and lightly knead together. Don't forget the dough must stay cool so wash your hands with cold water before you start. Knead the dough together very very lightly. Its almost like we are just compacting it in to a ball. Now wrap with kitchen membrane and place in the fridge for 30-40 minutes until the butter sets again.
Now that the dough has cooled, we can roll it in to a sheet that's approximately 3mm or 0,10 of an inch. Cut in to 5x2 Inch rectangles. Knead the cut-offs together and roll in to more sheets until you have 8-9 rectangles.
Separate the egg yolks from the egg white. Set the egg white aside as you will need it for the meringue. In a medium sized saucepan combine the water, sugar, corn-starch, salt and lemon zest. Set to medium heat and constantly stir until the sauce thickens. Don't let it boil. Once thickened add 3-4 table spoons of the thick sauce in to the egg yolks while constantly whisking. This will temper the eggs and avoid clotting. Now add the tempered egg yolks back in to the sauce pan and stir until smooth. Add in the butter and lemon juice and whisk until combined. Pour in to the baked pie shell and set aside to cool.
Fill, Bake and Drizzle
Place 1-2 teaspoons of Lemon Curd in the top centre of the dough rectangle. Make sure you have enough space to fold it in the middle and pinch the edges together with your thumb. Using a fork, seal the edges all around.
Make an egg-wash with 1 whole egg and 3-4 tablespoons of water. Whisk until smooth. Now paint the pop tarts until well covered and place in the oven at 175C or 340F for 30-40 minutes or until golden brown.
Let them cool for a bit and then prepare the lemon drizzle. Combine the powder sugar and lemon zest. Now add the lemon juice 1-2 tablespoons at a time until you get a thick clump free glaze. Drizzle over the pop tarts and let it set.