Heat oven to 190C/fan 170C/gas 5. Butter two 20cm sandwich tins and line with non-stick baking paper. In a large bowl, beat all the cake ingredients together until you have a smooth, soft batter.
Blitz the pistachios in a food processor until very fine. Add the self-raising flour and caster sugar to the nuts and blitz until completely combined. Add eggs, baking powder and milk and mix together.
Divide the mixture between the tins, smooth
the surface with a spatula or the back of a spoon, then bake for about 20 mins until golden and the cake springs back when pressed. Turn onto a cooling rack and leave to cool completely.
For the filling mix the soft cheese with the caster sugar and a few drops of vanilla essence.
Sandwich the sponges with the filling. For the topping, stir 2 tbsp water with 100g caster sugar in a microwaveable bowl and microwave on High for 3-4 mins until bubbling and starting to caramelise. Stir in a handful of roughly chopped pistachios then quickly spoon onto the cake. Keep in an airtight container and eat within 2 days.