mix the flour and salt together
cut the cold butter into pieces and work into the flour until its crumbly, use two knives or a pastry blender, or your hands
add enough of the water to the flour mix and stir to form a dough, if its still dry you can add more water, you don't want a dry dough
once a dough forms knead it lightly in the bowl and then transfer it to the counter
pat it out in a rectangle and then roll it out to 12x6 inches with the short end towards you
grate the frozen butter directly onto the bottom 2/3s of the dough
fold the top third down over the butter, then fold the bottom third up as well, see diagram
rotate 90° roll out to 12x6 inch rectangle again, fold the same way
cover tightly and refrigerate for 20 minutes
remove from the fridge, and put the short end towards you, roll out to 12x6 inch rectangle, fold the same as above and rotate 90°
roll out to a 12x6 inch rectangle again, fold again
wrap the dough back up and refrigerate
repeat the rolling and rotating one more time and the dough is done
to make the shells: roll the cold dough out to roughly 18x14 inches, cut 36 circles out of the dough
lay 12 of them on a baking sheet covered with parchment paper
cut the middles out of 24 of the circles
make an egg wash out of the egg and cream, use your finger to put a circle of egg wash on the flat full circle of dough, lay one ring on top, add egg wash, lay final ring on top, add egg wash, be careful not to get egg wash on the sides of the vol au vent shell, that can make it bake up uneven!
when all the shells are assembled refrigerate for 20 minutes
preheat the oven to 425°while the shells cool
bake the vol au vent shells for 15-19 minutes or until the shells are baked, the bottoms are crispy and they are lightly browned all over
cool completely on a wire rack
if any of the shells have risen inside the rings pick that out or poke it back down
TO SERVE fill with your desired filling, or use my blueberry filling idea, add a TBSP of jam to the shells, make the heavy cream into whipped cream and pipe into the tops of the vol au vent shells add a blueberry and sprinkle with graham cracker crumbs