Add cheese, flour, cornstarch, and salt to a food processor and pulse until just combined. about 25-30 seconds. add butter and process until the mixture has a wet sand consistency. adding the ice water and process again until the mixture starts to form into balls.
transfer the dough to a floured surface and divide it into 2 equal portions. flatten into 2 squares about 5x5 inches and wrap in plastic wrap before putting in the fridge to chill for about 1 hour and as long as 2 days.
Preheat the oven to 350°f. prepare 2 large baking sheets with parchment paper or silicone mats.
Use one section of the dough at a time (leave the second one in the fridge until you are ready for it) to roll out onto a floured surface into a 9-inch square. no need to be perfect at all.
using a pizza cutter or a sharp knife clean up the edges and trim them into an 8-inch square. then slice vertically into 1-inch slices then again horizontally into 1-inch squares. should leave you with 64 crackers.
Place the crackers on a prepared baking pan and use a skewer or large toothpick to poke a hole in the middle of each square. lightly sprinkle with additional salt if you want.
Bake for 16-18 minutes or until the edges are golden brown. rotating the pan halfway. for a crispier cracker bake for about 20 minutes.
Remove from the oven and allow to cool completely on the baking sheet before serving.
Notes
experiment with different cheeses and let me know in the comments what you used.