Preheat oven to 350 F. Have 2 baking sheets ready. You'll also need 3 pieces of parchment paper the size of a baking sheet: 2 to line the pans with, and one to put on top of the sticky dough when you roll it out.
Grind 2 teaspoons nigella seeds in a spice grinder for 5 seconds, just till roughly broken. Place all the dry ingredients (except the whole seeds for topping) into the bowl of a stand mixer and mix briefly. Add wet ingredients and mix together to form wet crumbs, about 30 seconds.
Transfer half the mixture onto a sheet of parchment. Using your hands, roughly press and shape the dough into a rectangle 1/2 inch thick. Sprinkle with extra whole nigella seeds and a little salt, then cover with a second sheet of parchment and roll the dough out to just under 1/4 inch thick. Straighten the sides with an offset spatula, patching as needed to maintain straight edges. Don’t worry if it’s a bit oily and crumbly, it’ll come together.
Using a pizza cutter or knife, cut the dough into 1-1/2 inch squares, making 3 cuts the long way and 5 cuts the short way. Use the small end of a chopstick to gently press a dot into each cracker. Use an offset spatula to gently lift and separate the crackers so they're not touching one another. Slide a baking sheet under the parchment, and repeat with second half of dough.
Bake crackers for 10 minutes, rotating pans halfway through. Crackers will barely turn golden around the edges, and will look dry and slightly puffed. Crackers will firm up more as they cool, so don’t be tempted to over bake them.
Cool pans on rack for 5 minutes, then remove crackers to cooling rack to cool completely. Store in an airtight container at room temperature.
Notes:
- To make egg white easier to measure, first beat lightly with a fork to loosen it up. Then pour into the measuring spoons.
- Recipe adapted from Against All Grain by Danielle Walker
