Pre-heat your oven to 160C Fan/180C/350F/Gas Mark 4 and grease and line a 12" x 9" traybake tin
Melt the butter and light brown caster sugar in a pan on a low heat until the butter is melted
Remove from the heat and add the white chocolate, leave it for a few minutes for the chocolate to melt, then stir together. Leave the mixture to cool for 5 minutes. Don't worry if it looks a little lumpy, it will go smooth again when you add the eggs
Whisk the eggs and vanilla extract into the mixture
Add the plain flour, whisk in until you can't see any flour
Pour the batter into the lined traybake tin and add blobs of the Biscoff spread all over. Use a butter knife to swirl it around a little bit - don't over mix
Bake for 20 minutes
Take the blonies out of the oven, press the Lotus biscuits into them, then put them back in the oven for 10 minutes, or until they are golden brown all over. Using a skewer inserted in the centre doesn’t give a clear indication that they are done because blondies are meant to be gooey and almost a little under cooked. Blondies are the white chocolate version of brownies and they are not like cake. They will also set more as they cool down, wait until they are cool to remove them from the tin and slice into pieces
Store in an airtight container in a cool place and eat within 3 days