Shape and Bake: On a very lightly floured surface, divide dough into 10 portions (about 95 grams each). Use your palm to press down on dough to release any air bubbles. Rotate your hand until dough starts to form a ball; turn your hand, and make a “C” shape. Keep dough under your palm, and continue rotating your hand and applying pressure in same direction until dough becomes a smooth, tight ball.
Press each ball flat into a 3-inch disk, and place on floured parchment paper. Cover and let rise in a warm, draft-free place (75°F/24°C) for 20 minutes.
Carefully drop buns, 2 to 3 at a time, into slow boiling water-baking soda mixture. Cook for 30 seconds; turn, and cook for 30 seconds. Using a spider strainer, remove from water, letting excess drip off, and place at least 1½ inches apart on prepared pans.
In a small bowl, whisk together egg yolk and remaining 1 tablespoon (15 grams) water. Brush buns with egg wash. Using a lame or sharp paring knife, score a 1-inch “X” in top of each bun. Sprinkle with sea salt.