Preheat your oven to 200ºC/180ºC Fan/Gas 7.
Line a baking tray with baking paper and add 300g of caster (superfine – US) sugar.
Heat in the oven for 7 minutes.
Meanwhile, measure 150g of egg whites in a mixing bowl and whisk to soft peaks using a mixer or handheld electric whisk. Whisk slowly to begin with then increase the speed to medium until soft peaks form – about 5 minutes.
By now your sugar will be hot so you can remove it from the oven and add it to the whisked egg whites a spoonful at a time.Keep whisking until the mixture is thick, glossy and bright white – about 7-9 minutes.
Meanwhile, turn your oven down to 100ºC/80ºC Fan/Gas 1/2.
You can check the mixture is done and all the sugar has dissolved by rubbing some of the mixture between your fingers. If you can feel any grain, continue to whisk for a couple more minutes until it feels completely smooth.
At this point, you can add a teaspoon of pink powder food colouring if you want to. Mix into the meringue until you have a soft pink effect.
Trace a circle smaller than your cake stand on two pieces of baking paper. Stick the baking paper to a baking tray using a few dots of meringue mixture.
Split the meringue mixture evenly onto the baking trays using the circles as a guide. The meringue will spread slightly in the oven but not much.
Put the baking trays in the oven and bake for about an hour or until the meringue discs can be easily lifted away from the baking paper without cracking.
Once baked, switch off the oven and leave the door open until the meringues are cool. Don't be tempted to take them out and remove them from the trays too early or they will crack!
While the meringues are cooling cut 100g of strawberries into small pieces and crush them with the back of a fork. Transfer them to a sieve and run the back of the fork over the crushed strawberries to get the juice out.
Add 2 tablespoons of blackcurrant cassis to the strawberries and add caster sugar to taste (about 2 teaspoons). If you don't have any blackcurrant cassis just add a tablespoon of water.
Whip 500ml of double cream until it has only just thickened. The cream should be soft and pillowy but not so thin it runs off a spoon. Do the drop test by picking up a spoonful and dropping it back into the bowl. If it plops gently it's whisked just right.
Set a few whole strawberries aside and cut the remaining strawberries into quarters. When the meringue discs are cool, spread the first disc with cream, add a drizzle of strawberry sauce and top with half the strawberries and raspberries.
Add the next meringue disc on top and repeat with cream and sauce.
Pile the remaining fruit on top and finish with slithers of pistachios and a few dried rosebuds if desired.