Preheat the oven to 160c and line a 9 inch square cake tin with parchment.
In a large bowl, beat the butter, sugar & vanilla until smooth.
Add the custard powder & plain flour and press into the tin.
Bake for 25 minutes.
Once the shortbread is baked, make the caramel.
Add the ingredients to a large saucepan and place over a low heat, stirring until the sugar is dissolved.
Once dissolved, boil until golden and thickened, stirring constantly and ensuring the caramel doesn’t catch on the pan.
Pour over the shortbread and leave to cool for an hour.
Once cooled, melt the white chocolate with the cream smooth over the caramel layer.
Add the chopped custard creams, sprinkles and chill for a couple of hours before slicing!
