This recipe has less sugar than many galette recipes, so while juicy and naturally sweet it does come off as just a touch tart. I love this and think the natural flavor of the plums really shine, but if you think you may like your galette a bit sweeter, try 1/4 cup sugar for the filling instead. If you haven’t used rye flour, it’s lovely in pie doughs and quite easy to work with. The directions below use the food-processor method to make the dough. If you’d prefer using a pastry cutter or your hands, that works, too. I prefer not to in the summer just because it’s not and I can never seem to work quite quickly enough. But, as always, do what makes you happy.
In a food processor, add the flours, salt and sugar and pulse once to combine. Add the cubed butter and pulse until the mixture resembles very coarse meal with some small butter pieces intact the size of small peas. Slowly sprinkle in the ice water, a tablespoon at a time, until the dough just barely comes together. Turn the dough out onto a sheet of plastic wrap or wax paper. Gather it together into a flat disk, wrap, and refrigerate for 1 hour.
Preheat the oven to 375 F. Line a rimmed baking sheet with parchment paper or a Silpat. On a lightly-floured surface, roll out the dough to an 11-inch round and transfer it to the baking sheet. In a small bowl, whisk egg and 1 tablespoon water together to create egg wash. Set aside.
In a medium-sized bowl, combine the plums, sugar, cornstarch, orange zest, and ginger bits. Toss well. Arrange the fruit in the very center of the dough circle, leaving at least 1 1/2 inches all around the border. Fold the exterior edges towards the center of the galette. Don’t worry about it looking perfect or neat–it shouldn’t. Chill galette in freezer (or refrigerator if your baking sheet won’t fit in the freezer) for 20 minutes.
Retrieve from freezer, brush edges with egg wash and sprinkle with sugar. Bake for 45-55 minutes, or until crust has turned golden brown and juices are bubbling and thickening. Allow to cool for at least 1 hour before serving (the fruit juices will firm up as it cools so you won’t have a runny galette). Store covered at room temperature for 2-3 days.