In a large mixing bowl, whisk together the flour, kosher salt, black pepper, sugar, garlic powder, and rosemary.
Add the cold butter and cut it into the flour mixture using a pastry cutter or fork until the mixture resembles coarse crumbs.
Stir in the finely shredded smoked Gouda until evenly distributed.
Add 3 tablespoons of ice water and mix until the dough begins to come together. Add additional water 1 teaspoon at a time only if needed. The dough should hold together when squeezed but should not feel wet.
Shape the dough into a disk, wrap tightly in plastic wrap, and refrigerate for 30 minutes.
Preheat the oven to 350°F (175°C). Line two baking sheets with parchment paper.
Roll the chilled dough on a lightly floured surface to approximately 1/8-inch thickness.
Use a pizza cutter or sharp knife to cut the dough into squares, rectangles, or desired shapes.
Transfer the crackers to the prepared baking sheets, spacing them slightly apart. Prick each cracker with a fork and sprinkle with flaky sea salt if desired.
Bake for 15 to 18 minutes, rotating the pans halfway through baking, until the crackers are lightly golden and dry to the touch.
Allow the crackers to cool on the baking sheets for 5 minutes before transferring them to a wire rack to cool completely. They will continue to crisp as they cool.