• Pre-heat the oven to 180C / 360F. Line a 9-inch square cake tin with baking paper. ensure there is enough to overlap the sides to make it easy to lift out the slice later.
• Place the Weetbix crumbs, flour, baking powder, cocoa powder, desiccated coconut and brown sugar into the Thermomix bowl. Mix for 10 seconds / speed 6. Set aside.
• Add the butter, golden syrup and vanilla extract to the bowl. Melt for 3 minutes / 60 degrees / speed 2.
• Return the dry ingredients to the bowl. Mix for 10 seconds / speed 4.
• Scrape down the bowl and repeat: 10 seconds / speed 4.
• Tip the mixture into your lined baking tray. Use a spoon to press the mixture into the tin and smooth over the surface.
• Bake in the oven for 15 minutes.
• Remove from the oven and leave to cool completely in the tin.

For the icing

• Add the icing sugar and cocoa powder to the Thermomix bowl. Mix for 5 seconds / speed 9.
• Add the butter and boiling water to the bowl. Mix for 20 seconds / speed 5.
• Scrape down the bowl and repeat: 10 seconds / speed 5.
• Spread the icing over the cooled slice and use a spatula to smooth it down, ensuring you cover the slice evenly and completely.
• Sprinkle over the desiccated coconut then transfer to the fridge and leave to cool for 30 minutes.
• Use the baking paper to lift the slice out of the tin. Use a sharp knife to cut the slice into 16 equal portions.