I tried googling it both ways and got better results as one word vs. two, which is why I went that way. I don't actually speak German, other than to order buns in a bakery. And even then, only if you want 10 of them.
Do you know if there's a special technique to form the double crust?
Combine the dry ingredients and mix thoroughly, using a whisk (or similar instrument)
Using a stand mixer with paddle attachment, combine the liquid ingredients and add to the dry (keep the mixer speed low to prevent a flour dust cloud) and mix until all ingredients are well combined and now raw flour is visible and the mixture begins to pull away from the sides of the mixing bowl.
Replace paddle attachment with kneading hook sprayed with cooking spray or coated with olive oil. Knead the dough on a low speed (about #2 on most stand mixer speed adjustments) for 5 - 8 minutes; you are looking for a dough that it tacky but not sticky.
Scrape the dough from the mixing bowl and form a ball, then place the ball into a lightly oiled bowl and cover with plastic wrap. Set aside in refrigerator for 6 - 12 hours. Remove from the fridge and gently degass (using finger tips), then allow to rest at room temperature environment (approx. 70 degrees) until nearly but not fully doubled in size. Remove the dough from the bowl and work the dough into a ball; pull and stretch the dough by stretching the sides of the ball down and folding the dough ball into itself at the bottom.
Continue until the surface of the dough is smooth, then place the dough ball onto a floured surface or onto a parchment paper lined baking sheet - form the loaf, cover with lightly oiled plastic wrap and set aside at room temperature for final proofing.
When the dough has nearly but not yet doubled in mass, brush the loaf with a light coating of oil and dust generously (but don't' smother it) with flour. Preheat oven to 450 degrees.
Load the loaf into the oven and spray oven interior with mist of water. Repeat the misting every 15 - 20 seconds for the next two minutes, making a deliberate effort to wet the top of the loaf.
llow the bread to bake 10 - 15 minutes, then rotate it 180 degrees and continue baking until the internal temperature is 205 - 210 degrees.
Remove to cooling rack and allow to cool at least one hour before slicing.
There are other recipes e.g. http://b2bb2c.info/agriculture/anyone... that you might also want to consider. Although this one lists a "sourdough" starter, it is actually a poolish. But It may interest you.