In a large bowl mix flour and salt until fully combined and place it into the freezer for 5-10 minutes
Cut cold butter into small chunks and place it into the freezer for 5-10 minutes
Once all ingredients are nicely chilled, add very cold butter chunks into flour and rub the mixture between your fingers until it becomes a sand like consistency.
Add very cold water into the dough, a small amount at a time, and stir with a spatula or wooden spoon after each addition
Start working the dough with your hands. First, it will look crumby but it should come together in the next minute or so. No need to knead the dough, stop mixing it as soon as it comes together. Remember, leave in some butter chunks, do not overwork the dough, and do not use a mixer
Form a disk, cover it with plastic wrap and let it rest in the fridge for a minimum of 2 hours
After 2 hours, take the pie dough disk out of the fridge and let it rest few minutes on the kitchen counter. The dough should stay cold but slightly warmed up to be able to roll it out without breaking it
The easiest way if you roll the dough on or in between two silicone baking mats. With the help of a rolling pin roll the dough into a rectangle of 42x30 cm / 16x12 inches Alternatively, transfer the dough to a lightly floured surface and start rolling it out into a rectangle of 42x30 cm / 16x12 inches. No need to add too much flour while rolling, the pie dough should be cold enough not to stick to the kitchen counter. If at any point the dough gets too warm, pop it back into the freezer to chill for a minute then continue
Check the size of your muffin pan holes. The diameter of the dough circle should equal the size of the muffin tin holes (from the back) in the following way: 2x side + 1x bottom, in my case is was 11 cm / 4 inches
With the help of a cookie cutter, cut out circles of the dough that will fit your muffin pan holes
Flip your muffin tin and slightly press down the dough on the cavities of the tin.
Chill the pie dough again now in the freezer for 10 minutes
Pre-heat oven to 200 C / 372 F (no fan)
Take the cupcake tin out of the freezer and bake the mini pie crust in the following way: 20 minutes on the tin, then carefully remove them from the tin, apply a light egg wash (egg yolk + milk), and bake for further 5 minutes
The pie crust is ready when it is baked even golden brown