2 cups all-purpose flour, plus more for dusting
½ cup grated Parmegiano-Reggiano
½ teaspoon kosher salt
12 tablespoons (1 ½ sticks) cold unsalted butter, shredded
¼ cup plus 2 tablespoons, or more, cold water
1 ½ cups fresh basil leaves
2 cloves garlic, minced
¼ cup pine nuts
¼ cup extra virgin olive oil
4 medium heirloom tomatoes, cut into ¼-inch thick slices
8 ounces fresh mozzarella, drained and cut into 3/16-inch thick slices
Fleur de sel
Freshly ground black pepper
Combine the flour, ¼ cup of the Parmegiano, and kosher salt in a food processor and pulse a few times to combine. Add the butter and pulse until the mixture resembles coarse crumbs. Add the water and pulse until the dough just comes together. Test the dough by squeezing a small amount together with your fingertips. If the dough holds together, it’s ready. If it’s crumbly, add up to 1 more tablespoon of water and pulse 2 more times. Transfer the dough to a work surface, bring together into a ball, and then flatten into a disc. Wrap in plastic wrap and refrigerate for about 20 minutes.
Combine the basil, garlic, pine nuts, 3 tablespoons of the oil, and remaining ¼ cup of Parmegiano in the food processor and pulse until smooth.
Preheat the oven to 425˚F. On a lightly floured surface, roll the dough to a 13×17-inch, 3/16-inch thick rectangle. Roll the dough up on the rolling pin and transfer it to a parchment-lined baking tray. Refrigerate for about 10 minutes.
Spread the pesto evenly in the center of the dough rectangle, leaving a 2-inch border at the edge, and layer the tomatoes and mozzarella on it, arranging them in neat, overlapping rows. Fold the edge of the dough over the tomatoes and mozzarella, pleating it as you go. Refrigerate for another 10 minutes.
Lightly brush the tomatoes and mozzarella with the remaining 1 tablespoon of oil. Bake for 25 to 27 minutes, or until golden brown. Let cool slightly. Sprinkle generously with fleur de sel and pepper, cut into portions, and serve.
Makes 1 large crostata, serving 6 as a vegetarian main course. Wonderful drizzled with Aceto Balsamico Tradizionale di Modena. Drain the mozzarella thoroughly on paper towels so that there's no excess moisture to turn the crust soggy. It's not absolutely necessary to wash the food processor between the crust and pesto.