5½ cups bread flour, plus more as needed
2 tablespoons granulated sugar
2½ teaspoons kosher salt
1 tablespoon active dry yeast
4 tablespoons unsalted butter, at room temperature
Finishing:
⅓ cup baking soda
1 large egg
1 tablespoon whole milk
Coarse sea salt for finishing
Make the Dough: In the bowl of an electric mixer fitted with the dough hook attachment, mix the flour, sugar, salt and yeast to combine, about 30 seconds. Add 1½ cups warm water (about 95°F to 100°F) and the butter, and mix on low speed until the dough comes together, about 3 minutes. Increase the speed to medium-high and continue to mix until the dough is very smooth, about 4 minutes more. Lightly grease a large bowl with nonstick spray, and transfer the dough to the bowl. Cover loosely with plastic wrap or a damp towel and let rise at room temperature until double in size, 1 hour to 1½ hours. Turn the dough out onto a lightly floured surface. Divide the dough into 8 even pieces. Cover the dough loosely with plastic wrap or a clean kitchen towel and let rest on the work surface for 10 minutes. Shape the Pretzel Rolls: Working one at a time, cup your hand over a piece of dough and roll it in a circular motion on the work surface to form it into a tight round. Cover the rolls loosely with plastic wrap or a clean kitchen towel and let rise on the work surface, 45 minutes to 1 hour more. Make the Baking Soda Solution: Preheat the oven to 425°F and line two baking sheets with parchment paper. Bring 6 cups water to a simmer over medium heat and then stir in the baking soda. Working in batches, add two or three buns to the water at a time. Soak, gently flipping once or twice, for about 1 minute. Using a wire strainer or slotted spoon, gently drain the buns and transfer them to the prepared baking sheets, staggering to leave room for the buns to rise and spread. In a small bowl, whisk together the egg and milk to combine. Using a pastry brush, gently egg wash each bun all over, then sprinkle with the coarse salt. Use scissors to cut an X shape into the surface of each roll. Bake until the pretzel buns are deeply golden brown, 18 to 22 minutes. Cool at least 20 minutes before serving warm, or cool completely.