In a food processor (or using a pastry cutter), combine the shredded cheese, flour, cornstarch, and salt. Add the cold butter and pulse or cut in until the mix looks like coarse crumbs.

Drizzle in the cold water and pulse (or stir) until the dough just comes together. If it’s still dry, add a teaspoon more water at a time.

Form the dough into a disc, wrap it in plastic wrap, and chill for at least 30 minutes. This makes it easier to roll out.

Preheat the oven to 350°F (175°C). Roll out the dough on a lightly floured surface until it’s about 1/8-inch thick. Cut into small squares (a pizza cutter works great!). Use a fork to poke holes in the center of each square.

Place crackers on a lined baking sheet. Sprinkle with sea salt if using. Bake for 13–15 minutes or until the edges are just golden. Let them cool on the baking sheet—they’ll crisp up more as they cool.