1. Preheat the oven to 375°F and line two baking sheets with parchment paper.

2. In a large bowl, mix the flour, Parmesan, rosemary, kosher salt, black pepper, and garlic powder.

3. Cut in the cold butter until the mixture looks like coarse crumbs.

4. Add the ice water one tablespoon at a time, mixing until the dough just comes together.

5. Shape the dough into a disk, wrap it, and chill for 20 to 30 minutes.

6. Roll the dough on a lightly floured surface to about 1/8 inch thick.

7. Cut into small squares or rectangles and place them on the prepared baking sheets.

8. Prick each cracker with a fork.

9. Brush the tops lightly with beaten egg and sprinkle with flaky sea salt.

10. Bake for 14 to 17 minutes, or until golden around the edges.

11. Cool completely before serving so the crackers crisp up fully.