Preheat the oven to 180C/350F and grease and line an 8x8 inch square pan. I used Wilton Bake Easy and grease proof paper. Leave to one side.

Place melted butter, sugar and vanilla into a large bowl and whisk until well combined and smooth. Mixture will be pale brown and thick.

Add in the egg and mix until well combined.

Add in funfetti, salt, baking powder and salt and whisk until a you have a thick, smooth batter.

Add in the broken up Oreo's and fold in gently with a spoon.

Tip into your prepared pan and spread into an even layer with the back of a spoon/spatula.

Place in the oven for 22-27 minutes, until risen slightly, golden and the top looks matte when the oven light hits it. An inserted skewer into the centre will have a few crumbs on, but not liquid batter. The edges will come out clean when you insert a skewer.

It's important not to over bake the blondies as they will set when cooling and may become like rocks if over baked!

Leave to cool in the pan completely, before transferring to a cutting board to slice into 9-12 bars.

Birthday Cake Blondies will keep in an airtight container, at room temperature, for 5 days.