I have made soft pretzels in the past, and have always enjoyed them, however I have always wanted to make a sourdough version. After much internet research, I did not come across any recipes that called out to me, so I decided to do my own. I adapted a Bertinet recipe, simply replacing fermented white dough in the recipe with an equal quantity of firm sourdough starter. I also retarded the dough in the fridge over night... though this was more to do with the fact that I wanted to bake them fresh the next morning rather than anything else.
All in all I was really pleased with the result. The inside was very soft and authentic. I didn't bother with either a lye bath, or boiling the pretzels prior to baking. I plan to try boiling the next time I make these, but the lye bath seems a little to much trouble.
By the way, I will be happy to post the whole recipe if anyone is interested.