Crisp Cornmeal-Cheese Wafers

Set oven racks in the upper- and lower-middle positions and heat oven to 375 degrees. Line 2 large (18 by 13 inches, or similar) baking sheets with a nonstick liner such as parchment paper, and set aside. In a food processor, pulse the flour, cornmeal, salt, pepper, and baking soda to combine. Add the Parmesan and Romano cheeses and pulse to combine. Add the butter and process until the mixture resembles coarse meal. With the motor running and the feed tube open, pour the buttermilk through the feed tube and process until the dough forms a ball, about 20 seconds. Transfer the dough to a floured surface, knead it a few times until it is smooth and uniform, cover with plastic wrap, and set aside to rest for 15 minutes.
Working with a quarter of the dough at a time, roll it out evenly to about 1/8 inch thick. Use a 2-inch cookie cutter to make rounds from the dough, then arrange them (with 1/4 inch between rounds) on the baking sheets. Once the sheets are filled, bake the crackers until crisp and golden, 9 to 12 minutes, rotating the sheets front to back and top to bottom about 5 minutes into the baking time. Remove the crackers to a rack and cool thoroughly; repeat to finish baking the remaining dough. Store the wafers in an airtight container at room temperature for up to a week.