01 - Preheat the oven to 375°F.
02 - In a bowl, combine flour and salt. Cut in the cold butter until the mixture resembles coarse crumbs. Add ice water, 1 tablespoon at a time, mixing until the dough just comes together. Shape into a disk, wrap, and chill for 20 minutes.
03 - On a lightly floured surface, roll out the dough to fit a 9-inch tart or pie pan. Press into the pan and trim excess. Prick the base with a fork. Line with parchment and fill with pie weights or dried beans.
04 - Bake crust for 15 minutes. Remove parchment and weights, and bake for 8-10 minutes more until lightly golden. Set aside.
05 - Heat olive oil in a skillet over medium heat. Add leek and sauté 2-3 minutes until soft. Add asparagus and sugar snap peas; cook for another 3-4 minutes until just tender. Stir in spinach and cook until wilted. Remove from heat.
06 - In a mixing bowl, whisk eggs, milk, heavy cream, salt, pepper, and nutmeg until fully combined.
07 - Spread the sautéed vegetables evenly over the baked crust. Sprinkle with Gruyère and feta. Pour the egg mixture over the top.
08 - Bake for 30-35 minutes, or until the center is set and the top is lightly golden.
09 - Cool for 10 minutes before slicing and serving.