Start by pre-heating your oven to 180c. Also grease and line a 9 inch square cake tin, leave this aside.

In a pan or pot, add the blueberries, sugar and lemon juice. Mix all this together.

Place this onto medium heat and cook, whiles stirring every now and then, until the blueberries soften. This might take 5-10 minutes.

Add the corn flour/water and mix this in. Keep heating whiles stirring, until the mixture thickens. Leave this aside to cool down.

In a pot, add the unsalted butter and the white chocolate. Place this onto medium heat and heat until melted. Once melted, leave aside to cool down slightly.

In a large bowl, add the sugar and lemon zest. Rub these together using your fingers, this is going to bring out the lemon flavour.

Add the eggs and vanilla to this. Whip these together until the mixture lightens in colour and increases in volume. This should take about 2 minutes.

Add the melted chocolate and butter mixture into this, whisk until combined.

Now add the lemon juice, plain flour, salt and baking powder. Whisk these in.

Pour this batter into your prepared cake tin, then bake in your pre-heated oven for around 25 minutes.

Whiles the blondie is baking, make the crumble. In a bowl, add all the ingredients for the crumble. Mix until clumps form, then leave aside until ready to use.

Once the blondie has baked, add the blueberry filling on top of it. Spread this out.

Now add the crumble on top, add as much or as little as you want of this.

Place this back into your oven and bake for around 20 minutes, or until the crumble on top starts to brown.

Once baked, leave to cool down at room temperature for about 20 minutes, then place this into your fridge to chill and set up for AT LEAST 1 hour.

Once it has chilled, dust some icing sugar on top of it, then cut it into pieces and enjoy!