In a food processor, pulse the parmesan, flour, and butter until it resembles sand.
6 ounces 2 cups parmigiano reggiano, 3/4 cup all purpose flour, 4 Tablespoons rosemary butter*
Slowly pour in one tablespoon of water at a time while pulsing the dough. The dough should begin to clump together in a ball. Add another 1/2 Tablespoon if needed. Do not add too much water, or the crackers will be soft, and the dough will be too sticky.
2 Tablespoons cold water
Using your hands shape the dough into a disk that is about 1 inch thick. Wrap the disk in plastic wrap tightly. Freeze for 30-40 minutes or refrigerate for 3-4 hours.
After the dough has chilled, preheat the oven to 300 degrees. Lightly flour a clean surface and rolling pin. Unwrap the dough and flour each side.
Roll out the dough so it is rectangular in shape and about 1/16 inch thick. It doesn’t have to be perfect. The thinner the crackers are the crunchier they will be.
Using a sharp knife or pizza cutter, cut the rolled dough into 1.5-inch squares. Sprinkle with flaky salt and rosemary if desired. Gently press the toppings into the dough so they stick.
flaky salt & rosemary, optional for topping
Line two baking sheets with parchment paper. Transfer the crackers to the lined baking sheets.
Bake the crackers for 25-30 minutes, rotating the sheets about halfway through. The longer you bake them, the crunchier they will be. Let cool completely on the baking sheet before serving. Store in an airtight container for 3-4 days.