1. Whisk the flour, 3/4 cup of the finely grated Parmesan, chopped rosemary, garlic powder, fine sea salt, and black pepper together in a large mixing bowl (or pulse in a food processor) until evenly combined.

2. Add the cold cubed butter to the bowl and cut it into the dry ingredients with a pastry cutter or your fingertips until the mixture looks like coarse crumbs with a few pea-sized bits of butter remaining.

3. Drizzle in the cold water a tablespoon at a time, gently tossing with a fork until the dough begins to clump together and holds when pressed. If the mixture still looks dry, add up to 2 tablespoons more water, just until it comes together.

4. Turn the dough out onto a lightly floured surface and press it into a flat disk. Wrap it tightly in plastic wrap and chill for 20–30 minutes while you preheat the oven to 375°F (190°C). Line two baking sheets with parchment paper.

5. On a lightly floured surface, roll the chilled dough into a rectangle about 1/8-inch thick, keeping the thickness as even as possible. Use a pizza cutter or sharp knife to cut the dough into small squares or rectangles and transfer them to the prepared baking sheets.

6. Use the tip of a skewer or a fork to poke 2–3 small holes in the center of each cracker to keep them from puffing too much in the oven.

7. Brush the tops of the crackers lightly with olive oil, then sprinkle with the remaining Parmesan, a few extra rosemary leaves, and the flaky sea salt.

8. Bake for 12–15 minutes, rotating the pans halfway through, until the crackers are deeply golden around the edges and the centers are set.

9. Let the crackers cool completely on the baking sheets or on a wire rack; they will crisp up even more as they cool. Store in an airtight container at room temperature for up to 4–5 days.