In another bowl, with a wooden spoon or in a stand mixer (using the dough hook), combine 690 ml (2 3/4 cups) of flour and the salt. Stir in the yeast mixture and mix on medium speed until a soft ball forms. Add the remaining flour if the dough seems too sticky. Knead for 5 minutes.
Shape into a ball and place in a clean and lightly oiled bowl. Cover the bowl with a damp cloth and let rest in a warm and humid place for about 1 hour. Divide the dough into 8 equal pieces.
For each pretzel, on a floured work surface, roll a piece of dough into a thin cylinders, about 60-cm (24-inch) long. Form a U with each cylinder and cross the two ends twice in the top third. Bring the two moistened ends to the base of the U and press to hold them in place.
Place on a floured baking sheet. Cover with a clean cloth and let rise for 30 minutes at room temperature.
With the rack in the middle position, preheat the oven to 200 °C (400 °F). Line a baking sheet with parchment paper.
In a large pot of simmering water, poach 2 pretzels at a time, for about 1 ½ minutes on each side. Drain and place on the baking sheet.
In a bowl, combine the egg and milk (egg wash).
Brush the pretzels with the egg wash. Sprinkle with coarse salt. Bake for about 25 minutes or until golden brown. If desired, serve with yellow mustard.