Begin by cubing the butter, then placing in the freezer. While the butter chills, get out your food processor, measure flours, grate cheese, fill a small bowl with water and ice cubes.
After about 10 minutes, place butter, cheese, flours, and garlic powder in your food processor. Pulse to combine but don’t go crazy.
Now, begin adding the ice water, 2 tablespoons at a time, pulsing in between each addition. Once you reach 4 tablespoons, pinch a little of the dough between your fingers, it should stick together. Add more water as needed, we want all the flour incorporated, and the dough should resemble small pebbles. I ended up using 6 tablespoons.
Pour the dough out onto a large piece of plastic wrap. Use your hands and the edges of the plastic wrap to form the dough into a flat disc. Wrap tightly and refrigerate at least one hour.
Prepare two cookie sheets with parchment paper or silicone baking mats. Flour your work surface and rolling pin. Bring out the chilled dough and cut in half, returning half to the fridge while you work.
Roll out the dough as thin as possible, I used a layer of parchment paper underneath and a layer of plastic wrap on top to prevent the dough sticking to the rolling pin. The thinner the cracker, the crispier.
Cut into 1 inch squares. By this point, my dough was getting soft, so I had to wipe the knife in between each row.
Using a spatula, carefully transfer the cut crackers on a parchment-lined cookie sheet. Don’t just use the perfect squares, bake all the rough edges too, you’ll be grateful for every cracker you get. Sprinkle the crackers with a couple pinches of salt.
Put the tray in the fridge and repeat with remaining half of the chilled dough. Once you put the first batch in the fridge, preheat the oven to 350 degrees.
When the oven is ready, place the chilled crackers on the center rack. Put the second batch of cut dough back in the fridge to chill.
Bake each batch about 15 minutes. Keep in mind, baking times will vary depending on the thickness of your crackers, so set a timer for 10 minutes and go from there. The end result we are going for is deep golden brown all over, not just brown edges and pale centers, this will lead to soft crackers. For example, in this picture, the top tray wasn't baked as long, and while they are still delicious, the lower tray has the perfect crunch. The difference is subtle, but worth the extra minute in the oven!
Allow crackers to cool completely, this is the hardest part. Store cooled crackers in an airtight container.