For the crispbread: Preheat the oven to 400 degrees F.
In a mixer on low speed, combine the flours, sugar, baking powder and salt. Pour in the melted butter, then slowly pour in 1 1/2 to 2 cups water, 1/4 cup at a time, until a soft, sticky dough forms.
Dust the counter and rolling pin well with flour, and roll the dough into a rectangle about 1/4-inch thick.
For the topping: In a small bowl, mix together the sesame seeds, poppy seeds, garlic, onion and coarse salt. Whisk together the egg with 2 tablespoons water and brush a thin layer over the crispbread dough. Sprinkle the topping mixture evenly over the top. Use a wheeled pizza cutter or pie crimper to cut the dough into medium-sized rectangles (it's okay if the shapes are irregular). Using a spatula, carefully transfer the crispbreads to a lightly floured baking sheet (they won¿t spread, so it's fine to leave little room between them). Using a fork, lightly prick the surface of each of the crispbreads.
Bake in the center of the oven until the edges become golden brown, 10 to 15 minutes. (Bake time will vary depending on the size and thickness of the crackers, so keep an eye on them!) Once golden, allow to cool 5 minutes, then move to a wire rack until completely cool. Package in clear cellophane bags tied with decorative ribbon.