For the Starter:
Combine the flour, water, salt, and yeast, and ferment overnight (or 12 to 16 hours).
For the Pretzel:
Combine the flour, beer, and water in a bread mixer; let the mixture rest for 20 minutes. Add the yeast to pre-ferment. Start mixing the dough slowly with the starter, adding the salt and butter in pieces. Mix on the first speed for 3 minutes; all butter, salt, and yeast should be fully incorporated. Mix on second speed for 6 minutes, stopping halfway to scrape the bowl. Bulk ferment the dough for 2 ½ hours. Divide and shape the dough into 4-ounce portions, or 8-ounce portions for a baguette. Twist the dough into pretzel shapes and allow them to rest on a parchment- or silicone baking mat-lined sheet pan.
To Assemble and Serve:
While the Pretzels rest, bring water to a boil in a large stainless steel rondeau. Add enough baking soda to create fizzy bubbles. Boil the pretzels until they float (about 1 minute); flip them over and boil for about seconds 30 more. Coat the Pretzels with the egg wash and sprinkle with salt. Bake in the preheated oven on a lined sheet tray for 8 minutes; rotate and bake for another 8 minutes, or until golden brown.