Preheat oven: Set your oven to 200°C/fan 180°C/gas 6.
Prepare plums: Place the plum halves, cut-side up, in a shallow roasting dish. Pour over 100ml of cold water and sprinkle with ground ginger.
Roast: Roast for 10-15 minutes, or until slightly softened but still holding their shape. Check after 10 minutes, as cooking time may vary depending on plum ripeness.
Add crumbs: Remove the plums from the oven and sprinkle with the majority of the chopped Hi-fi bars, concentrating them on the cut sides.
Finish roasting: Return the plums to the oven for 3-5 minutes, or until the crumbs are warmed through and begin to caramelize.
Serve: Serve the plums with fat-free Greek-style yogurt, a drizzle of the roasting juices, and the remaining Hi-fi crumbs.
Note: For a healthier option, consider using a natural sweetener like stevia instead of the Hi-fi bars.