In a mixing bowl, combine the warm water, sugar, and instant yeast. Allow this mixture to sit for about 10 minutes until it becomes frothy.

In the bowl of a stand mixer, mix all-purpose flour and fine sea salt on low speed to combine.

Pour melted butter and foamy yeast mixture into the bowl while the mixer is running on low.

Increase the mixer speed to medium-high and knead the dough. Add extra flour if necessary until the dough achieves a smooth, tacky consistency.

Weigh the dough for accuracy and divide the total weight by 8 to determine each bun's weight.

Roll each piece into a ball and pinch together at the bottom.

Place the balls on a tray, cover with plastic wrap, and let rest for 15-20 minutes.

Flatten a ball into a 5-inch disk and roll it into a 7-inch log.

Position the rolled buns seam side down on a lined baking tray and cover with plastic wrap.

Let them rise for another 15-20 minutes.

Preheat the oven to 450°F and prepare a baking tray with parchment paper.

Bring 8 cups of water to a boil, adding baking soda gradually.

Place 2-3 buns into the simmering water, blanch for 20 seconds, then flip and blanch for another 20 seconds.

Remove the buns, place them on the prepared tray, and brush with egg wash. Sprinkle with coarse sea salt.

Make 3 diagonal cuts on each bun and bake for 10-12 minutes until golden brown.

Transfer to a cooling rack for 10-15 minutes before using.