Preheat the oven to 180°C.
Grease a 35x25cm Swiss roll tin with butter and line with baking paper.
Whisk the egg whites in a clean bowl until soft peaks form.
Gradually whisk in 275g of caster sugar until the mixture is smooth and glossy.
Spoon the meringue into the tin, level with a palette knife, and sprinkle with lemon verbena leaves.
Bake for 8 minutes at 180°C, then reduce to 170°C and bake for 10 minutes until crisp.
Turn the meringue onto a clean tea towel, peel off the paper, and cool.
Simmer plums with 100g sugar and 100ml water for 10 minutes until softened.
Whisk the double cream to soft peaks, adding the remaining sugar and lemon curd.
Spread lemon cream over the meringue, leaving a 1cm border, and top with most of the plums.
Roll the meringue tightly starting from the long end using the towel.
Transfer to a platter and garnish with remaining plums and verbena sprigs.