Place flour, salt, and butter in a food processor and pulse until fine crumbles form.
Add ½ cup of the ice water and pulse until dough forms. If it still seems dry add additional water, 1 tablespoon at a time.
Dump out onto a clean surface and form into a disc shape and wrap in plastic wrap.
Refrigerate for at least 1 hour.
To make the blueberry filling:
After dough has chilled, make the filling.
In a large bowl, combine blueberries, sugar, honey, lemon zest, and cornstarch and mix to combine.
To assemble:
Preheat oven to 400 degrees F.
Roll out your galette dough onto a floured surface until it is about ?” thick. I usually just eyeball this. With a galette, you don’t have to make sure it fits into a pie dish so you don’t have to make sure it is perfectly round. You can cut some of the crazy edges off if you want.
Place rolled out galette dough onto a baking sheet lined with parchment paper.
Dump blueberry filling in the middle of the dough and spread out evenly. You want to leave some room for the crust.
Fold over dough edges approximately 1 inch, folding/pleating the dough as you go.
Brush edges with lightly beaten egg and sprinkle with sugar.
Bake in preheated oven for 40-45 minutes, until edges are golden.