Preheat the oven to 200C/180C Fan/Gas 6. Line an 8″ Square baking tin.
In a medium saucepan combine the butter, brown sugar and golden syrup and heat on low until the butter has melted. Turn off the heat and stir in the oats.
Pour the oaty mixture into the baking tin and press down. Bake for 20-25 minutes until golden brown at the edges (it's fine if still a little wobbly in the centre). Let cool on a wire rack.
Once cooled, melt the white chocolate in 20 second intervals in the microwave. Pour over the flapjack base.
Remove the filling of two passion fruits into a sieve over a bowl - leaving you with a small bowl of juice and a sieve with the pips. Keep the pips to one side to decorate later.
Combine the passion fruit juice and icing sugar. Use a spoon to pour the juice in horizontal lines about an inch apart. Use a knife or skewer to run in the opposite direction, creating a feathered effect.
Sprinkle over some of the passion fruit pips. Let set in the fridge for an hour. Then let come back to room temperature to slice and serve!