Whisk 4 egg whites until stiff, then whisk in a tsp powdered ginger, a tsp cornflour and 80 g caster sugar in stages
until stiff and glossy again. Stick a sheet of baking parchment to a baking tray with a dot of meringue at each corner,
then spoon the meringue onto the parchment in a circle about 28-30cm in diameter (trace the outline of a dinner plate as a guide),
peaking up at the edges. Bake in a 150°C oven for 90 minutes. Turn the oven off and leave to cool for several hours. Meanwhile,
cut rhubarb into 3-4cm chunks and place in a shallow dish. Add 2-3 balls of stem ginger, chopped into small dice, together with
some of the syrup from the jar. Sprinkle over a Tbs or two of caster sugar and bake in the oven for 15-20 minutes then allow to cool.
To serve, whip double cream to stiff peaks, spread over the meringue and top with the rhubarb.