Dissolve sugar and yeast in warm water. Let proof for 5 minutes, or until foamy.
Stir in 2 cups of flour. Add salt and butter. Mix well. Add 2 additional cups of flour and knead until smooth and elastic, adding flour as needed.
Cut the dough into 18 pieces. Take each piece of dough and form a ball by pulling the sides to the center and pinching to seal. Then place it on the counter, pinched side down. Lightly cup your hand around the dough ball, rotate your hand in small circles lightly pressing and rolling the ball around in the palm of your hand until the surface is smooth and tight.
Place roll on parchment lined baking sheets, at least 1 inch apart. Cover and let rise until doubled, about 30 minutes.
Preheat oven to 425F. Boil 2 quarts of water and dissolve baking soda in water. Reduce temperature to a simmer. Poach each piece of dough for 20 seconds, then flip and poach 20 seconds more. Remove from water with a slotted spoon and blot the bottom of the spoon with a kitchen towel before returning the rolls to the prepared pans, seam side down.
Brush the rolls thoroughly with egg wash. Slash the tops with sharp knife making an "X" in the top. Sprinkle with coarse salt, if desired. Let rise, about 20 minutes. Bake 15-20 or until deep golden brown. Cool on a rack.