Place rolls in the oven and bake till golden brown. While rolls bake, prepare the final 6 rolls as above.
Heat milk, water, and butter to 120F. (49C)
While milk warms, mix sugar, salt, yeast and 1/2 of the flour, in bowl of mixer.
Add the warmed milk to the flour mixture and mix till well incorporated and smooth. Add remaining flour and mix with dough hook for 10 minutes or till dough passes window pane test. Add slightly more flour if dough seems sticky.
Turn dough out and fold a few times. Put in a greased bowl, turn dough to coat the top, cover and let raise till doubled.
Preheat oven to 375
Portion the dough into 12 pieces, approximately 81 grams each.
Pat a portion into a square. Fold 3 ways like a letter, fold again in half and seal edges. Roll lightly until about 5 inches. Allow to rise for about 20 minutes.
Make an egg wash with the egg yolk and 1T water.
Bring 8 cups of water to a boil. Add the baking soda and reduce heat to slow boil. Place 2 portions in the water for about 30 seconds. Turn and allow to remain for 30 more seconds. Remove with spider. Place on silicone mat on a baking sheet.
When 6 portions have been boiled, baste with egg wash, score the rolls, and sprinkle with some of the coarse salt (optional, to taste).