Melt the butter and white chocolate together in microwave gently.
Stir in the vanilla, salt & marshmallows until the mixture becomes stringy.
Add the malty cornflakes and the sprinkles, stirring well.
Spread onto the chilled base evenly.
Top with more marshmallows, malty cornflakes & sprinkles pressing gently so they stick.
Place into the fridge for a few hours. Cut and enjoy!