Mix frozen blueberries and potato flour in a large bowl and make sure the potato flour does not clump.
Whisk together all the dry ingredients. Then work the butter into a sandy dough and then add the eggs in batches. Divide the dough into 2 parts and plastic. Leave to cool for 1 hour.
Set the oven to 170 degrees.
Take out the doughs and knead smoothly. Roll out two rounds. Cut paper and put in the bottom of the mold. Place a round in the mold and press the dough just over the edge. Save leftover dough.
Stir in the blueberry bowl and pour the blueberry into the mold. Lay the other round and pinch the dough together on the edges.
Whisk egg white and water a little by hand. Brush the pie and sprinkle over a thin layer of sugar. Bake in the oven for about 40 minutes.
Vanilla sauce: Stir together egg yolk and sugar in a bowl. Divide the vanilla bars lengthwise and scrape out the seeds. Cream up cream, milk, vanilla seeds and rods.
Beat half of the liquid over the yellows and whisk together until slightly dissolved.
Pour the liquid back into the saucepan and stir with a slice pot over heat until the sauce has reached 84 degrees and thickens. Pull the sauce aside, mix the sauce with a stick mixer and strain into a bowl. Contact plastic and let cool in refrigerator for 2 hours.
