In a large bowl, stir together flour and salt. Using a pastry blender or your hands, cut in butter until coarse crumbs form. Using a fork, stir in ice water, 1 tbsp at a time until a soft dough can be formed into a ball. Shape dough into a disk and wrap in plastic wrap. Refrigerate for 45 minutes to an hour.

Preheat oven to 375F.

Roll out dough on a lightly floured surface into a 13" circle. Transfer dough to a 9" deep pie plate, trim the excess dough leaving ½" overhang. Fold the overhang underneath and use your knuckles and thumbs to pinch the dough around the rim to form a decorative edge.

Line the dough with a piece of parchment paper and fill with pie weights or dried beans. Bake for 18-20 minutes. Remove from oven and carefully remove parchment. Cool completely.

In a large pan, heat butter over medium heat. Add onion, saute for 4 minutes. Add broccoli florets and cook for another 4 minutes or until softened and partially cooked. Set aside and cool completely.

In a large bowl, whisk eggs with cream, cheddar cheese, Parmesan and Dijon mustard. Stir in cooled onion and broccoli mixture. Pour filling into cooled shell and bake at 375 for another 40-45 minutes or until set.