In a medium glass or Pyrex bowl or measuring cup, place the yeast, 1/2 tablespoon of sugar, and 1/4 cup of lukewarm water. Proof the yeast: it should show signs of life by expanding. slightly bubbling, or moving. If none of these things happened, the yeast is dead. Spill out and restart.
Meanwhile, in the bowl of a stand mixer fitted with a dough hook, on medium-low speed, mix the 1.5 tablespoons sugar, 1 cup of water, sea salt and oil. (This can be done by hand with a whisk t00)
When the yeast has “proofed,” beat the yeast mixture into the mixing bowl. With the mixer at a low speed, add the flour. Raise speed to medium and knead for 4-5 minutes until a nice, smooth, satiny dough forms. It will have almost a matte finish. If you are kneading in the flour by hand, it may take a few minutes longer to get a good, smooth texture. Cover the bowl of dough with a kitchen towel and allow the dough to rise in a warm place for 1 1/2 hours, or until doubled in size.
Preheat the oven to 350*. Line a jelly roll (or cookie sheet) with parchment paper. Set aside.
Remove the dough to a lightly floured surface. If the dough is sticky, knead in flour, a little bit at a time, until the dough is easy to roll. Divide the dough into 3 balls and roll each into a long strand. Braid each challah using 3 strands of dough. Place on prepared cookie sheet. Set aside while you prep the next step.
Bring 8 cups of water and baking soda to a boil in a pot with the widest opening. Gently and carefully, lower one challah into the baking soda solution. Using 2 wooden spoons (or you arm…), carefully turn the challah so both sides get equally covered in to water or bathe the top with spoonfuls of the solution. Remove after 30 seconds and place on the parchment lined pan.
Brush the top with some water from the pot and then top with salt or sesame seeds.
Bake for 30 minutes. Best served warmed or re-warmed. Serve with mustard. (Honey mustard was my favorite!)