Transfer the flour on your worktop and use the bowl to make a well in the middle. Fill it with the mushroom powder, the sugar, the salt, the water, the olive oil and the egg yolk. Then mix it and knead it into a nice ball of dough. If you feel like the dough is to soft add a little bit more flour. Now let it rest in your fridge for at least 30 minutes.
After that flour your worktop and roll out the dough until it’s 2 to 3 millimeters thin. Then cut it with a small round cutter. Now spray a little bit of oil spray on some small tartelettes molds and place the dough on 2/3 of the molds. Shape them and then place another mold on top. After place another on top. In total you can stack two to three tartelettes.
Then bake them at 170 °C for around 20 minutes. Now when still hot remove the tartelettes from the mold to prevent them from breaking. Keep them dry and covered.