In a large bowl or the bowl of your stand mixer, mix the flour and yeast. Then add the milk, sourdough discard, melted butter, and malt syrup and stir or use the paddle attachment until combined.
3 cups (375 grams) all-purpose flour, 1 teaspoon (3 grams) instant yeast, ⅔ cup (160 milliliters) milk, 113 grams unfed sourdough discard, 2 tablespoons (28 grams) butter, 2 tablespoons (42 grams) barley malt syrup
Add the salt and knead the dough for about 8 to 10 minutes by hand or 5 to 7 minutes with your mixer's dough hook until it is smooth and elastic.
2 teaspoons (10 grams) Kosher salt
Cover the bowl with plastic wrap and let the pretzel dough rise in a warm place until doubled in size, about 1 to 2 hours.
To make the baking soda bath, combine two or three cups of boiling water with a tablespoon of baking soda per cup of water in a pyrex or baking pan big enough to hold the pretzels one at a time. Stir until the baking soda has dissolved.
2 to 3 tablespoons Baking soda
Preheat oven to 425°F (220°C) and line a baking sheet with parchment paper.
Divide the pretzel dough into eight roughly equal-sized portions and roll each into a rope 18 to 24 inches in length. If the dough is very elastic and springy, set your rope aside to rest and move onto the next.
Shape the ropes and put the shaped pretzels onto a baking sheet lined with parchment paper or a silicone mat. They can be spaced relatively closely, but don't let them touch.
Working one at a time, dip each pretzel into the baking soda bath, flip it over, and then transfer back to the prepared baking sheet. Cover the pretzels loosely with plastic wrap, and heat your oven to 450°F (230°C) while the pretzels are rising, about 30 minutes.
Right before baking, brush the pretzels once or twice with the egg wash and sprinkle with the coarse salt or flaky sea salt. Bake until deep golden brown, about 12 to 14 minutes.
1 egg, Coarse pretzel salt or flaky sea salt
Let cool slightly before serving. Enjoy!