01 -
Place the chopped rhubarb into a wide pan with caster sugar and 2 tablespoons of water. Cook on a medium heat, stirring frequently, for about 10 minutes, or until the rhubarb breaks down and turns jammy. Set aside to cool. If using powdered custard, prepare according to package instructions and set aside to cool.
02 -
Preheat the oven to 180°C (160°C fan). Butter the baking tin and line with baking parchment.
03 -
Place the butter and both sugars in a medium pan over low heat. Melt together until smooth and glossy, then remove from heat and cool for about 10 minutes.
04 -
In a large bowl, sift together the flour, custard powder and baking powder.
05 -
Beat the eggs into the cooled sugar and butter mixture, then fold in the dry ingredients until you have a smooth batter. Stir in 150g of white chocolate chips and vanilla extract.
06 -
Pour the batter into the prepared baking tin. Use a teaspoon to swirl the rhubarb on top of the batter. Add dollops of custard, then swirl a skewer or toothpick through the rhubarb and custard to create a marbled pattern.
07 -
Bake for 40-50 minutes until set and the edges are coming away from the sides of the tin. If the top begins to brown too quickly, cover with kitchen foil. Leave in the tin to cool, then transfer to the fridge for minimum 2 hours or overnight.
08 -
Melt the remaining 100g of white chocolate and drizzle over the cooled blondies. Cut into equal squares and serve.