Line a cookie sheet with parchment paper; set aside. In a mixing bowl stir together the all-purpose flour, corn tortilla flour, sugar, baking soda, and the 1/4 teaspoon kosher salt. Using a pastry blender cut in butter until mixture resembles coarse crumbs. Make a well in center of flour mixture. Add buttermilk. Using a fork stir until mixture can be shaped into a ball.
Turn the dough out onto a lightly floured surface. Knead for 8 to 10 strokes or until dough is almost smooth. Divide dough into 6 portions. Roll each portion into a 9x6-inch free-form rectangle (1/8 inch thick). Use a pastry wheel or knife to cut rectangles into quarters. Using a fork, prick rectangles well. Place 1 inch apart on prepared cookie sheet.
Lightly brush crackers with water. Sprinkle with peppercorns and the 2 to 3 teaspoons kosher salt; press into dough. Bake in a 375 degree F oven about 15 minutes or until crisp. Remove from cookie sheet to wire racks; cool. Store in airtight container at room temperature up to 1 week. Makes 24 oversize crackers (24 servings).