Place the shredded cheddar, flour, garlic powder, cornstarch, Parmesan cheese, and salt in a food processor. Pulse for about 30 seconds until they are well combined.

Add the cold butter cubes and pulse for another 20 seconds until the mixture looks like wet sand.

Add the cold water and pulse until the dough begins to form clumps. If the mixture is still too crumbly after adding the water, add 1 teaspoon more water at a time until the dough comes together.

Transfer the dough onto a lightly floured surface, shape it into a square, and wrap it in plastic.

Refrigerate the dough for 45 minutes to firm it up before baking.

Preheat your oven to 350°F. Roll out the chilled dough to about 1/8 inch in thickness. Cut the dough into 1-inch squares. For a classic look, use a skewer or toothpick to poke a small hole in the center of each cracker and sprinkle flaky salt on top.

Place the crackers on a baking sheet and bake for 17-20 minutes until they turn golden around the edges. Remove from the oven and let cool completely before serving.