To make the krautburger dough:

1. Measure out the sugar, then sprinkle a pinch of it into a small bowl with the warm water and yeast. Stir to dissolve, then set aside for about 5 minutes until the yeast is foamy.
2. Heat the milk in a small pan until you see bubbles at the edges. Cut up the 4 tablespoons of butter, then stir it into the hot milk to melt along with the rest of the sugar. When the butter is melted, crack in the eggs and beat them until you get a smooth mixture.
3. Mix the flour and the salt in a large mixing bowl or a stand mixer, then make a well in the center. Pour the milk/butter mixture into the well, then the yeast mixture.
4. Stir the ingredients with a wooden spoon to make a shaggy dough.
5. For kneading, by machine, switch to the dough hook on a stand mixer and let the mixer run on low speed until you get a smooth, sticky, elastic dough, about 5 minutes To knead by hand: turn the dough onto a lightly floured surface, and use a bench scraper to slap the dough down, then bring the edges towards the center. Repeat this motion for 10 minutes, until you have a smooth, elastic dough. Resist the urge to add more flour. This should be a soft dough, and most of the stickiness will go away after the dough has risen.
6. Cover the dough with plastic wrap and set aside to rise for 1 hour. Meanwhile, make the filling.

To make the krautburger filling:

1. In a large skillet or dutch oven, melt the bacon fat over medium heat.
2. Add the ground beef and allow to sear for a couple minutes, then use a spatula to break up the meat. Add in a little bit of your salt, then cook until the meat is no longer pink.
3. Remove the beef to a plate or bowl with a slotted spoon.
4. Add in the onion and shallot and move around the pan with the spatula until the onion is soft and translucent.
5. Pop in the garlic, paprika, marjoram, pepper, and allspice and scrape around the pan for about 1 minute until you can smell the garlic.
6. Throw the cabbage in and turn it to coat with the onions and spices briefly.
7. Add in the rest of the salt and
8. Cover the pan and cook for no more than 2-3 minutes. Taste the cabbage at this point. It should be crisp tender, but do not cook it further.
9. Mix in the sauerkraut and green onions and cook for 1 more minute.
10. Turn off the heat and spread out the filling to cool on a sheet tray in one layer.

Assembling the krautburgers:

1. Preheat the oven to 375 F (190 C).
2. Place parchment on 2 sheet trays.
3. Divide the now soft and puffy dough into 24 pieces. Cover the dough to keep it from drying out as you work.
4. Roll each piece into a little ball and set aside on a work surface. Keep them in order. By the time you finish rolling the last ball, the first ball will be ready to make into a krautburger.
5. On a floured surface, roll a piece of dough into a circle about 4 1/2″ across.
6. Using a measuring cup, scoop out 1/3 cup of the filling into the center of the flattened dough circle.
7. If you're using cheese, add in about 1 tablespoon of cheese on top the filling.
8. Use your hands to pinch the edges of the dough into the center. This dough is very soft and forgiving, so it will pinch together easily.
9. Turn the krautburger over, then turn it over on your work surface. Form your hand into a dome, then turn the krautburger around clockwise and few times. This will neaten up the edges and make a nice round shape.
10. Place the finished krautburger on one of the prepared sheet trays. Continue making krautburgers, covering them with a tea towel or greased plastic wrap as you go. By the time you finish the last one, they'll be ready to bake.
11. Beat the egg white and water and brush all the krautburgers with egg wash. Sprinkle the tops with everything bagel seasoning if you like. If you're using cheese, I like to sprinkle a little bit of cheese on top as well.
12. Bake for 25 minutes until golden brown.
13. Serve with whole grain mustard.