Method

1. Preheat oven to 180° C Fan and line a 8” x 8” loose base square baking tin with grease proof baking. Make the baking paper is hanging over the edges of the tin to help remove the blondies when baked.
2. Break the custard creams in half, and use them to line the base of the tin, making sure the custard cream logo is facing downwards. How many you need will depend on how many you place in the tin (watch the video for visual reference here). Alternatively, you can use whole custard cream biscuits instead of the halves. 
3. In a stand mixer with balloon whisk attachment or bowl with electric hand whisk, add in the aquafaba. Whip on medium / high speed until fluffy, then add in the sugar a-little at a time, whipping on high for at least 5-8 minutes or until it becomes thick and glossy.
4. In a saucepan, add in the vegan white chocolate, coconut oil and vanilla. Heat on low until melted. Use a heat proof spatula to prevent the chocolate from sticking and burning to the pan. Alternatively, you can use a bain-marie method or microwave to melt.
5. Pour the melted chocolate mixture into the whipped aquafaba and fold together using a spatula.
6. Sift in the flour, custard powder, cornstarch, baking powder and bicarbonate soda. Fold everything together until there is no dry ingredients showing. 
7. Add in the broken up custard cream biscuits and 100g of chopped white chocolate. Fold through. 
8. Pour the blondie batter into the tin on top of the biscuits, making sure not to disrupt the biscuits too much. Carefully spread this out nice and even using a off-set spatula. 
9. Place the tin into the middle of the oven and bake for 30 minutes. If you want a more fudgey blondie, you may want to underbake by a few minutes!
10. Once baked, remove the tin from the oven and allow to cool fully on a wire rack. TIP: Keep the blondie in the tin while it’s cooling. This will help it keeps it’s shape and will also lock in some of the moisture, which will help with the chewy texture.
11. Use a sharp knife to cut the blondies into little bars. Cut the blondies so each has a custard cream biscuit on top.
12. Serve and enjoy!