You will see the egg whites become firmer and glossier as the sugar melts.

The unrequired egg whites could be whisked into meringue.

In a saucepan, mix the egg whites with the caster sugar and coriander over a very low heat until all the sugar has dissolved.

Add the rest of the egg whites with the cocoa powder and continue whisking until it forms stiff peaks.

Sift the cornflour and cocoa powder together, then gently fold into the egg whites with the vinegar until combined.