Pulse pecans in a food processor until consistency of a course meal. Add the pecans, flour, sugar, salt, cinnamon to a large mixing bowl und combine. Add butter cubes, then rub in with your fingers until the mixture looks like fine crumbs. Add the ice water and combine everything to a dough. Place in plastic wrap and let it cool in the fridge for about 60 minutes.
Toss strawberries, blueberries, raspberries, vanilla, brown sugar, corn starch and balsamic vinegar in a bowl. Roll out dough on a lightly floured surface to a 10-12" round. Carefully transfer to a parchment-lined baking sheet. Mound berry-filling in center of dough, leaving a 2" border. Fold edges over, overlapping slightly. Brush dough with egg wash and sprinkle with brown sugar.
Bake until filling is bubbling for 45-50 minutes. Let cool before serving.