Dissolve the fresh yeast in the warm water and add the salt, softened butter, and both types of flour. Use the dough hook on your hand mixer to combine everything into a smooth dough. After 5 minutes, transfer the dough to a work surface and knead it with your hands for another 10 minutes. Put the dough in a greased bowl and allow it to rise in a warm place for 90 minutes.
Divide the dough in half and roll out one half into a circle. Transfer the dough to a greased, ovenproof dish and let it rest for another 30 minutes. Use a fork to poke holes all over the dough and bake it for 12 minutes at 400°F. Once it's out of the oven, allow it to cool off a bit.
Sweat the onions in olive oil and add the sauerkraut, beer, and caraway seed. Let everything simmer for 10 minutes before grating in the potato. Season with salt and pepper, let everything simmer for another 5 minutes, and then allow the sauerkraut to cool down a bit.
Fry the beer brats in a pan. Then spread a layer of sauerkraut filling over the baked pie base.
Spread the fried beer brats over the sauerkraut, making sure to reserve some for later. Cover the brats with the rest of the sauerkraut.
Divide the second part of the dough in half. Roll out one half so it's long and narrow, spread the shredded Swiss cheese down the middle, and seal the dough by pinching it together.
Repeat the same process with the other half of the dough, but instead of using cheese, chop up the remaining beer brats and spread the pieces across the dough.
Twist the cheese crust onto itself and place it on the edge of the sauerkraut pie. Form a pretzel out of the dough filled with brats and place it on top of the sauerkraut pie.
Boil the baking soda with the water. Once the mixture has cooled a bit, generously brush it over both pieces of dough and sprinkle coarse sea salt on top. Transfer the dish to the oven and bake at 425°F for 14 minutes.
