Mustard is a must on these, as well!
20 oz. all-purpose flour
12 oz. warm water, about 105°-115°F
2 oz. butter, melted and cooled slightly
2 tsp. kosher salt
2 tsp. sugar
1 package (2 1/4 tsp.) active dry yeast
For the topping
salt (bigger flakes are better)
For the boil
2 quarts water
1/3 c. baking soda
Sprinkle the yeast over the warm water and allow it to sit for a few minutes to hydrate.
Combine the dry ingredients in the bowl of a stand mixer fitted with the dough hook, and start stirring on low to combine. Add the water and melted butter, and when the dough ball has come together, switch to kneading speed for 5 or 6 minutes, until the dough is uniform and elastic. Turn out onto a lightly floured surface, form into a ball, then place in a large bowl that's been sprayed with oil and cover lightly with plastic wrap and a tea towel. Let rise in a warm spot for about an hour, until doubled. At this point I was headed out for the afternoon, so I put them into the fridge for a few hours to retard any further rising (lactobacillic fermentation should have kept on going, though, which helps with flavor, so I'm fine with that).
Punch down gently and turn out onto a lightly floured surface. Divide into 16 equal pieces (divide into quarters, then divide each quarter into quarters). Shape each piece into a ball by "pinching up" the sides and then rolling against your work surface in your cupped hand. Place the formed balls onto oiled baking sheets, cover, and let rise again until almost doubled.
Preheat your oven to 425°F, with racks on the upper and lower middle positions.
Bring the two quarts of water to a boil, then add the baking soda. When the foaming subsides, boil the risen dough balls 2 or 3 at a time, 30-60 seconds per side, then remove them with a slotted spoon to 2 baking sheets dusted with cornmeal (I just reused the same baking sheets I proofed the dough on; didn't even bother to clean the oil off before adding the cornmeal). They'll be a little strange, but don't fret!
Whisk the egg and a little water together to make a wash, and brush the dough balls with it. Sprinkle on a little salt, and cut a few slits in the top to allow steam to escape. Bake for 15-20 minutes, until evenly mahogany brown. Serve warm with mustard or use as a hamburger bun for your favorite sandwich!