In a large bowl with a hook attachment, add 3 cups flour, 2 teaspoons instant yeast,1 ½ tablespoons sugar, and 1 ½ teaspoons salt, then whisk to combine. Add ¾ c sourdough discard, ¾ c lukewarm water, and 2 tablespoons melted butter. Mix with the dough hook.
Knead all the ingredients with a dough hook for about 8 minutes or until the dough is soft, smooth, and elastic. (10-12 min for kneading by hand) If the dough doesn't come together after 1 min, add 1 teaspoon of water at a time until it is no longer craggy. Dough should not be sticky
Shape the dough into a ball, cover and let it rest and rise for 1 -1 ½ hours or until noticeably puffy and nearly doubled in size.
Once the dough has risen, prepare the water bath. Add 12 cups of water and 1/2 cup of baking soda to a large pot and heat over the stove until the water reaches a steady boil, with bubbles breaking across the surface but the water not churning or splashing.
Preheat the oven to 400℉ (204℃)
Prepare 1-2 baking sheets with parchment or a baking mat.
Gently punch down the dough on a work mat or flat surface and cut it into 8 pieces.
Roll each piece into a rope about 24 inches long. Create a “U” shape, twist the ends together twice, bring the ends down to the bottom of the “U” shape and gently press the ends into the bottom.
Carefully lower each pretzel into the gently boiling baking soda bath for 30 seconds, flipping once halfway through. Remove with a slotted spatula or spoon, allow excess water to drain, and transfer to the prepared baking sheet.
If using pretzel salt or coarse salt, sprinkle the pretzels with the salt, directly after coming out of the water bath, while it's still wet.
Bake the pretzels at 400℉ (204℃) for 12-15 minutes or until golden on the outside.
Allow the pretzels to cool for 10-15 minutes to allow the interior to set (which allows for a better texture).