Sift the flours together.
To make the pastry crust, place the flours, sugar, salt, cream cheese, and butter in a food processor and process until the mixture resembles coarse breadcrumbs, about 20 seconds.
In a small cup, combine the water and vinegar. While the mixture is being processed, gradually add the water vinegar mixture until the dough comes together.
Turn the dough onto a floured surface and knead gently.
Wrap the dough in plastic wrap and chill for 60 minutes before rolling.
In a bowl, add the strawberries, rhubarb, lemon zest, sugar, and cornstarch. Toss with your hands to combine. Set aside.
Remove the dough from the fridge. Roll it out on a lightly floured surface to a circle of about 12 inches wide and ¼ inch thick. Move the dough onto a baking sheet lined with parchment paper.
Spread the mascarpone cheese on the dough and leave about 1 ½ inch border. Sprinkle 2 tbsps of almond meal on top of the mascarpone cheese.
Arrange the strawberry rhubarb mixture in the center of the dough leaving a one and a half inch border uncovered. Fold the dough edges over the filling pleating it loosely and leaving the galette open in the center. Patch the dough together if it breaks. Pour the juice into the galette. Refrigerate the galette for 30 minutes.
Preheat the oven to 375°F.
For the glaze, whisk the egg with heavy cream in a bowl. Brush the dough with the egg mixture and sprinkle the turbinado sugar over the whole galette.
When ready to serve, cut the galette into eight pieces, transfer them to a serving plate, and top with vanilla ice cream.