Step 1

In food processor, combine flour, Parmesan, sugar, salt, and pepper. Add butter and pulse until mixture resembles coarse crumbs (slightly smaller than peas). Pulse in 1 tablespoon sesame seeds and 1 teaspoon poppy seeds until combined. Continue to pulse, adding 3 tablespoons ice water, until dough is crumbly but holds together when squeezed. Pulse in additional ice water, 1 tablespoon at a time, if necessary; do not overmix. Form dough into 6- by 8-inch rectangle and refrigerate.

Step 2

Heat oven to 350°F. Let dough soften slightly at room temperature, 5 to 10 minutes. On lightly floured parchment paper, with floured rolling pin, roll out dough to about 11- by 13-inch rectangle. Slide onto baking sheet with parchment and freeze until firm, 15 minutes.

Step 3

Slide parchment with dough onto work surface and, using pastry wheel and ruler, cut dough into 1 1/4-inch squares. Slide onto rimmed baking sheet and grate remaining Parmesan over top with microplane. Sprinkle with remaining 1 tablespoon sesame seeds and 3/4 teaspoon poppy seeds. Bake, removing outer crackers as they are done if necessary, until golden brown, 20 to 25 minutes.