In a large bowl, whisk together flour, sugar, and salt. Add butter and, using your hands or spatula, mix together until pea-sized and some slightly larger pieces form. Add ice water, 1 tablespoon at a time, until dough starts to come together and is moist but not wet and sticky (test by squeezing some with your fingers). Mixture should be crumbly.
Turn dough onto a lightly floured surface and form into a ball. Flatten and form into a disk. Wrap the dough with plastic and chill in the refrigerator for at least 1 hour. You want the dough to be super cold.
In a clean bowl, combine peeled mandarin orange slices and toss with honey, pinch of salt, vanilla extract. Set aside.
Preheat oven to 400ºF and prepare a baking sheet by lining with parchment paper. On a lightly floured surface, divide dough to 6 equal pieces. Roll out each dough piece until it is about 1/4” thick. Transfer to baking sheet, leaving about 2” space in between each piece.
Arrange about 7-8 orange slices in the center of each dough piece, in a spiral direction, leaving about 1 1/2-inch border. Fold the edges towards the center, until all the edges are folded towards the fruit. Brush the edges with egg wash and sprinkle turbinado sugar (optional). Bake for 20-24 minutes or until the crust is golden brown and fruit is tender.