1-First, combine the flour, sugar, salt, pepper, and Parmesan cheese in a bowl, then mix in the butter until it looks shaggy. Gradually add ice water to form the dough, shape it into a disc, wrap it, and chill for 30 minutes.

2-After chilling, roll the dough into a rectangle, fold it into quarters, and chill for another 30 minutes; repeat this rolling and folding 2-3 more times for a flaky crust.

3-Next, prepare the zucchini by slicing it thinly, salting it, and layering it between towels to remove moisture for at least 30 minutes. Preheat your oven to 425°F and line a baking sheet with parchment paper. Roll the dough to about 15 x 20 inches and place it on the baking sheet; chill it until you’re ready to use.

4-Then, sauté the minced shallot and red pepper flakes in olive oil, and combine it with Dijon mustard. Spread this mixture on the dough, leaving a border, sprinkle most of the Gruyere cheese over it, and layer the zucchini slices with a slight overlap. Season with black pepper, brush the border with egg wash, fold up and crimp the edges, and brush the top with more egg wash.

5-Bake for 20 minutes, sprinkle the remaining cheese, and bake for another 10-15 minutes until the edges are golden and the crust is deep golden brown. Let it cool for 10 minutes, sprinkle with basil, slice, and serve. It’s best enjoyed the same day or kept covered at room temperature for one day. Total time includes 25 minutes of active prep, 1 hour 30 minutes for chilling, and 30-35 minutes of baking.