To crush the pretzels, add them to a food processor and pulse until you have coarse crumbs. I like to leave it a mix of sizes, with some of the pretzels being finely ground like bread crumbs and others being a bit chunkier.  If you don’t have a food processor, place the pretzels in a zip-top bag, press out the air and seal, and smash the pretzels using a rolling pin or kitchen mallet.