01 - Set the oven temperature to 350°F (180°C).
02 - In a large bowl, toss plums with granulated sugar, cornstarch, cinnamon, ginger, nutmeg, and lemon juice until evenly coated.
03 - Transfer the plum mixture into a 9-inch (23 cm) baking dish and spread evenly.
04 - In a separate bowl, mix flour, oats, light brown sugar, and salt. Incorporate cold butter cubes with fingertips until the mixture forms coarse crumbs.
05 - Evenly distribute the crumble topping over the plums in the baking dish.
06 - Bake for 35 to 40 minutes until the topping is golden and the fruit bubbles at the edges.
07 - Allow to cool slightly before serving warm, optionally paired with vanilla ice cream or custard.