For the crust: Place the flour, sugar and salt in a food processor and process to blend. Add the butter and pulse until the mixture resembles coarse meal. Add 3 tablespoons of the cold cream and pulse until the dough comes together in a ball. Add some or all of the remaining tablespoon of cream if the dough is still quite crumbly; it should hold together in a ball when you squeeze it. Place a large piece of plastic wrap on the counter, gather the dough into a ball and flatten the dough into a disk on the plastic wrap. Wrap well. Refrigerate for 1 hour.
Preheat the oven to 400 degrees F. Place a large sheet of parchment paper on a work surface and lightly flour the parchment. Place the dough on the paper, lightly flour the top and roll out into a round or oval about 1/4 inch thick. Transfer the paper to a rimmed baking sheet.
For the filling: Toss the plums with the crystallized ginger, flour, cinnamon and 4 tablespoons of the sugar in a large bowl. Arrange the plums in concentric circles on the center of the dough circle, leaving a 1 1/2-inch border of dough all around. Sprinkle the blueberries and any lingering pieces of ginger over and in between the plums. Fold the border in over the fruit. Distribute the butter pieces over the filling and sprinkle the border with the remaining tablespoon of sugar.
Bake until the crust is nicely browned and the fruit filling is soft and bubbling a bit, 40 to 45 minutes.
Warm the preserves in the microwave and gently brush the hot galette with the preserves, both the top of the crust edges and the fruit in the middle. Transfer the parchment paper with the galette to a wire rack and let the galette cool to room temperature. Transfer to a plate and serve with whipped cream if desired.
For this recipe, I used a Meyer lemon marmalade with ginger.