In the bowl of a stand mixer fitted with the dough hook, combine the flour, sugar, salt, and yeast.
With the mixer running on low, slowly add the warm water; mix briefly to incorporate.
Add the melted butter, and mix on medium speed for about 4 minutes. The dough will form a loose ball and pull away from the sides of the bowl.
Transfer the dough to an oiled bowl, cover with a clean, damp kitchen towel or plastic wrap, and let rise at room temperature for up to an hour. The dough will expand to a little more than double its original size.
Meanwhile, position a rack in the middle position of your oven and place the Baking Steel on top. Preheat oven to 450 degrees F for 45-60 minutes.
Turn the risen dough onto a floured work surface. Portion the dough into 6 equal portions (about 145g each) for pretzels, or 12 equal portions (about 70g each) for buns. Shape each portion into a pretzel (see note), or form them into balls to make pretzel buns.
Prepare the poaching mixture. Bring the water and baking soda to a boil; once the baking soda is dissolved, turn off the heat.
Using your hands, drop your pretzels into the poaching solution and let sit for about 10-15 seconds; flip with tongs, and repeat on the second side. Be careful: the mixture is hot, and can stain your clothes. Remove the pretzels with a slotted spoon so that the excess liquid can drain off, and place them onto a sheet of parchment paper. Coat generously with pretzel salt. Either place your parchment onto a sheet tray and place on your Baking Steel, or use a pizza peel to launch the parchment directly onto your Steel.
Bake for 10-12 minutes, rotating halfway through baking, or until golden brown (whether you’ve shaped them into pretzels or rolls, they will bake for the same amount of time). Remove from the Steel and transfer to a wire rack to cool. If you want, brush the pretzels with melted butter when you take them out for added flavor!
Store well wrapped leftovers for up to 3 days, or freeze for up to 1 month.