In a small saucepan, heat the milk (total of both milk amounts) and 1 teaspoon cane sugar until it reaches 95-110°F (it should feel warm to your finger, not hot.)
While the milk is warming, place the gfJules Flour and salt in the bowl of a stand mixer. Whisk on low to combine.
Once the milk is warm, add the yeast and gently stir. Allow the yeast to rest 5-10 minutes until it is bubbly and frothy.
Meanwhile, line a baking sheet with parchment paper. The baking sheet should be small enough to fit into your freezer.
Once frothy, add the yeast/milk mixture to the mixing bowl along with the melted butter. Mix the batter on low for 1-2 minutes. Scrape down the sides of the bowl and continue to mix the dough on medium-low for 2-3 more minutes.
Form the dough into a ball in the middle of the bowl. Cover and allow the dough to rest for 10 minutes while you gather the tools for the boil and work surface.
Lightly flour a work surface with more gfJules Flour. You don’t want too much flour, just enough to prevent the dough from sticking. Use a bench scraper or knife to divide the dough into 6 equal portions. Lightly flour your hands and roll each portion into a smooth, tight ball. Place each bun on the baking sheet. Oil a piece of plastic wrap and cover the buns. Allow them to proof in a warm location for about 45 minutes or until they are about double in size.
Once the buns have proofed, transfer them to the freezer for 10 minutes.
Meanwhile, preheat the oven to 395°F (convection -- preferred) or 425°F (static – buns will not get as dark). In a deep saucepan, bring 7 cups of water to a boil then add baking soda, 1 tablespoon at a time.
Remove the buns from the freezer. Working one at a time, place each bun into the boiling water and allow it to boil for 25-30 seconds, flipping the bun about halfway through. Using a slotted spoon, transfer the bun back to the lined baking sheet. Repeat until all the buns have been boiled.
Whisk together the egg yolk and 1 teaspoon water, then brush over each bun. Use a sharp knife to make an X score on top of each bun. Sprinkle with flakey sea salt, if desired.
Bake for 18-20 minutes on the top rack of your oven (not too close to the heating element, though). The internal temperature of the buns should be 205°F and they should be deeply browned on the tops. If baking on a static (not convection setting) the buns may take slightly longer to bake. Allow the buns to cool completely before storing in an airtight container.