I recommend using a stand mixer for this recipe as it is a stiff dough and can easily be kneaded in a stand mixer. If you don't have a stand mixer, you can still make these by hand (I've done it many times by hand, it will just take a bit of work to knead the dough - make sure you read my notes for this).Add sourdough starter, water, flour, sugar and salt to the bowl of your stand mixer and bring together to form a shaggy dough. Knead the dough (you'll need to use a dough hook for stand mixers) for around 10 minutes until it is smooth and supple. Be sure to give your stand mixer a break every few minutes so it doesn't over heat.This is a stiff dough (much like sandwich bread dough) so it won't be super elastic, however it should be smooth and not sticky. Once the dough is sufficiently kneaded, you'll need to allow it to rise, covered with plastic, at room temperature. You want the dough to rise around 50%.This dough is fairly low in hydration, so it will be a slower rise than a regular loaf of sourdough bread. Don't disheartened, just give it warmth and time. Once the dough has risen, you'll need to shape the pretzel buns.Divide the pretzel dough into 11 equal portions. I've done 11 x 80g portions, but you can make them bigger or smaller to suit your needs. Take each portion of dough and shape it into a little ball. I like to pinch the dough underneath to form a tight round ball, but you can also roll them if you prefer.
Cover the pretzel buns with a dish towel and allow them become lovely and puffy.
Once they are puffy, place them into the freezer for around 15 minutes to set.
While they are setting in the freezer, bring a pot of water with 60g of baking soda added to the boil and preheat your oven to 200C/390F.
When the water is boiling, carefully place 3 to 4 pretzel buns into the boiling water at a time. You want to boil them for around 30 seconds each. They should float to the surface and that's when you know to take them out.
Carefully remove the pretzel buns from the boiling water using a slotted spoon.Lay the pretzel buns onto a baking tray lined with baking paper. Using a pastry brush, brush on the egg wash mixture and then sprinkle with salt or seeds as desired. Use a sharp knife or lame to cut a small cross into the top of each bun. It doesn't need to be deep, just enough for the bun to open up in the oven.
Bake the pretzel buns for around 15 to 20 minutes at 200C/390F. Remove them from the oven when they are golden brown.
Allow them to cool before you enjoy them!