Preparation

1. Preparing the dough :
   
   In a large mixing bowl, combine the flour, hazelnut powder, Parmesan, vergeoise, fine Guérande salt and yeast. Add the butter in small cubes and knead vigorously by hand. Add the yoghurt and mix until you obtain a sandy texture.
   
   Divide the dough into four balls and leave to rest in the fridge for two hours.

2. Preparing the crackers :
   
   Preheat oven to 200°C. Roll out each ball of dough on a clean, floured surface until fairly thin (no more than 3mm). Sprinkle the dough with coarse grey Guérande salt, poppy seeds and sunflower seeds, and lightly press them into the dough. Using a notched roulette wheel, cut the dough into 5cm x 3cm rectangles.
   
   Line a baking sheet with parchment paper and place the crackers on it. Bake for 5 to 10 min, until crisp and slightly brown around the edges. If some are browning too quickly, remove them and leave those that need a few minutes longer!

3. Place crackers in an airtight container to keep them crisp.