Toast the pecans: Preheat the oven to 350 F and spread the pecans on a baking sheet.If they are raw, toast them for 10 minutes. If they are already roasted, toast them for five. This wakes up the flavor and makes them nice and crunchy. Make sure they are cool before they go into the filling.
Make the filling: Whisk together the sugar, syrup, melted butter and cocoa in a pot over medium heat until it’s smooth. Once it’s cool, fold in the vinegar, chocolate chips and pecans.
Assemble the galette: Preheat the oven to 400 F. Line a cookie sheet with parchment paper. On a lightly floured counter, roll out the dough until you have a circle that’s about 14-15 inches (diameter). Scoop the filling into the center and spread it out, leaving a two inch border. Fold the crust over onto the filling, don’t worry if it doesn’t look perfect but do make sure it’s tightly sealed so none of the filling can seep out. Brush it with egg wash and sprinkle sugar on top. Bake it for 30 minutes.
Serve warm, with ice cream.