Preheat the oven to Gas Mark 4 / 180ºc and line an 9x9" square tin with parchment paper.
Add the unsalted butter and white chocolate to a bowl and melt in short bursts in the microwave, stirring well each time, until smooth. (Ensure you stir well in between to stop it from splitting).
Once melted, stir in your caster sugar until combined (It may look like it has split but the eggs will bring it back together).
Add in the eggs and golden syrup and stir again until combined.
Mix through the plain flour and cornflour you can no longer see any flour.
Fold through your chocolate and lemon zest.
Pour the mixture into your lined tin, pipe on your lemon curd and blueberry jam and swirl through. I like to try and swirl it through to the middle so I get lemon curd and blueberry jam chunks in every bite! You can layer the blondie and pour half the mixture in, swirl some lemon curd and blueberry jam through then top with more blondie and jam.
Bake for 30-35 minutes (mine take 30 minutes), take them out the oven when there is an ever so slight wobble in the middle. (As these have a delicious amount of jam and curd in, they may take slightly longer to bake, keep an eye on them every 2-3 minutes).
Let the blondies cool in the tin fully, and then set the blondies in the fridge for 3-4 hours or overnight for best results!
Melt some white chocolate in a microwaveable bowl and drizzle over your blondie and sprinkle with lemon zest.
Slice your blondie into 9-12 slices and enjoy!
