Spoon large dollops of the mixture onto a baking tray lined with baking parchment, leaving space between each to allow for spreading. Place on the middle shelf of the oven, reduce the temperature to 140°C, fan 120°C, gas 1, and bake for 1 ¼ – 1 ½ hours, until firm to the touch. Remove and cool on a wire rack.
Preheat the oven to 150°C, fan 130°C, gas 2.
Whip the cream with the icing sugar until soft peaks form. Roughly break up the meringues and fold into the cream with 300g strawberries.
Using an electric hand mixer, whisk the egg whites in a large bowl until stiff peaks form. Gradually add the caster sugar, whisking continuously until stiff and glossy, then fold in the vanilla extract.
Spoon into 6 dessert glasses, top with the remaining 100g strawberries and serve straight away.