In a large bowl, whisk together the flours, sugar, onion powder, garlic powder, poultry seasoning, and salt.
Work in the shortening and butter until the mixture resembles coarse crumbs. Add 3 tablespoons water to the mixture and stir with a fork until the dough is evenly moistened. Add the fourth tablespoon of water and fold the dough over on itself with a bowl scraper until it comes together. Add another teaspoon of water to moisten any remaining dry spots, if needed.
Pat the dough into an 8" square (1/2" thick) on a sheet of plastic wrap. Wrap and chill on a flat surface for 30 to 45 minutes.
After chilling, unwrap the dough and cut it in half; place one piece of the dough on a piece of lightly floured parchment. Return the other piece of dough to the refrigerator until you’re ready for it. Preheat the oven to 375°F.
To make the topping: Stir together all of the topping ingredients.
Lightly flour the top of the dough and roll it 1/8" thick. Keep the edges as square as you can. Using a pizza wheel, cut the dough into a grid; the lines should be 1 1/4" apart.
Gather any scrap pieces from the outer edge of your grid and save to add to the second half of the dough when you roll it.
Prick each square once with the tines of a fork. Spritz the dough lightly with water and sprinkle the top lightly and evenly with the topping mixture.
Repeat with the second half of the dough.
Bake each pan of crackers for 13 to 15 minutes, until golden brown. Remove from the oven and cool on the pan; the crackers will become crisp as they cool.
Store any leftovers, well wrapped, at room temperature for up to a week; freeze for longer storage.