In a large mixing bowl add the flour, granulated sugar, diced butter, and egg.
Start rubbing the butter into the flour mixture until sand-like consistency forms.
Form a soft dough and roll it out on a lightly floured working surface.
In another bowl mix the diced peaches, cornstarch, sugar, and vanilla.
Spread the filling on top of the rolled dough and fold it lengthwise until all the sides are folded towards peaches, so the filling won’t spill while the galette is baking.
Bake the prepared galette in already heated oven at 350 F or 180 C degrees for about 30 minutes or until golden brown in color.
To serve, in a bowl mix the mascarpone cream, heavy cream, powdered sugar and scraped vanilla bean and dollop of the filling on top of each piece of the peach galette.