Directions

1. In a big bowl of an electric mixer with dough attachment, mix the yeast, sugar and warm water and let it sit until the yeast blooms, about 7 minutes.
   
2. To the mixture add 4 tablespoons melted butter, kosher salt, egg yolks, bread flour and flour and start the machine on low to knead until smooth, 15 to 20 minutes.
   
3. Take the dough out. Spray the bowl with cooking spray, set the dough back into the bowl and cover tightly with plastic wrap. Let rise on top in any warm, dry place for 1 hour, or until doubled in size.
   
4. Punch down the dough. Cut into 12 equal pieces and let rest for 5 minutes. In a medium saucepan, mix the baking soda and 4 cups water until it is milky, then bring to a simmer over low heat. Cover 3 baking sheets with parchment.
   
5. Roll each piece into a 2-foot-long rope. Lift the ends of the rope to make a "U," then cross one end over the other twice to make a double twist in the middle. Fold down the two ends and attach them to the bottom of the "U" to form a pretzel shape. Place on sheet pan. Repeat with the rest of the pretzels.
   
6. Working in batches, dip the pretzels into the simmering liquid for 30 seconds, flipping once. Remove using a spider and shake off any excess liquid; place on a prepared baking sheet. Lightly flour the pretzels, cover loosely in plastic wrap and let rise for 20 minutes. Preheat the oven to 425 degrees F.
   
7. Brush the pretzels with 4 tablespoons melted butter. Sprinkle with the coarse pretzel salt. Bake until browned, 8 to 12 minutes. Let cool for a few minutes and serve with mustard.