Add flour, cornstarch, and salt to a food processor. Pulse to combine.

Add cold butter and pulse until the mixture resembles coarse sand.

Add shredded cheese and pulse again until combined.

Slowly drizzle in cold water while pulsing until dough forms large clumps.

Shape dough into a 6-inch square, wrap in plastic wrap, and chill for 45 minutes.

Preheat oven to 350°F (175°C).

Roll chilled dough to 1/8 inch thickness. Trim edges and cut into 1-inch squares.

Use a toothpick to poke a hole in the center of each (optional).

Place crackers on a parchment-lined baking sheet and bake for 16–20 minutes until edges are golden.

Cool on a wire rack and sprinkle with sea salt if desired.