Whisk 300ml thickened cream, vanilla essence and icing sugar mixture together until thick. Cover and refrigerate.
Beat cream cheese, icing sugar & vanilla with a paddle mixer until smooth and slightly aerated. Add 225ml thickened cream and continue to beat until smooth. Add lemon juice and mix through.
Roughly chop strawberries in halves or quarters – add these and the raspberries to the mix, and mix again very briefly so berries are partly broken up and mixed in. Cover and refrigerate.
Preheat oven to 120°c
Place the egg whites into a clean and dry bowl that has been wiped with white vinegar. Beat with an electric whisk on a medium speed until it forms stiff peaks.
With your mixer still running, gradually add the caster sugar and salt, then whisk on a high speed for 7 to 8 minutes, or until white and glossy. To test whether it's done you can pinch some between your fingers – if it feels completely smooth it's ready; if it's slightly granular it needs a little more whisking.
Line 2 large baking trays with greaseproof paper. Divide the mixture between each tray, then use the back of a spoon to shape and swirl it across the trays, leaving a 3cm gap around the edges. Bake in the oven for 1 hour 10 minutes, or until crisp on the outside and a little soft and sticky inside. Once cooked, leave the meringues to cool.