Heat the oven to 150◦C/Gas Mark 2.
Draw a 20cm/8” circle on a length of parchment paper and place on a baking sheet ( pencil or pen mark underneath).
Whisk egg whites until very stiff and dry. Sieve and whisk in 87g sugar, continue whisking until the mixture is stiff and shiny.
Sieve another 87g sugar along with the cornflour in to the egg whites and fold through the mixture, along with the lemon juice and vanilla essence.
Spread some meringue on to the parchment following the shape of the circle. Build up into a bowl shape by swirling meringue round the outside of the shell.
Bake in the centre of the oven for 1 ¼ to 1 ½ hours until firm and delicately coloured.
Allow to cool before removing the parchment (the shell can be prepared in advance and stored in an airtight tin until required).
Combine 100g caster sugar with 300ml water in a small saucepan and heat through, stirring until the sugar has completely dissolved. Increase the heat to medium and simmer for 5 minutes. Add most of the blueberries to the hot syrup, reserving some for decoration, gently heating for a couple of minutes until they are just beginning to release some of their juices.
Remove the blueberries from the syrup and leave to cool. Boil the remaining syrup until it has thickened and reduced by about half. Stir in a slug of limoncello then set aside to cool.
Add the remainder of the limoncello to the double cream whip until the mix reaches the soft peak stage. Swirl the lemon curd through the cream then gently fold in the blueberries to create a rippled effect.
Pile the cream mixture in to the centre of the meringue shell.
Decorate with the reserved blueberries and drizzle the blueberry syrup across the top.
Finish with a grating of lemon zest across the top and a sprinkle of lemon thyme/mint leaves if required.