Preheat oven to 180°C fan bake. Line a slice tin (approximately 18cm x 28cm) with baking paper.
Place Weetbix, flour, Chelsea White Sugar, cocoa powder and baking powder in a large bowl. Mix to combine, then make a well in the centre. Add the melted butter and vanilla essence. Mix together, then press into prepared tin.
Bake for 10 minutes, until slice is cooked but still soft to touch in the centre. Ice while hot.
Icing: Mix Chelsea Icing Sugar, coconut and cocoa powder together in a bowl. Add butter, then gradually add enough hot water to melt butter, blending to form a spreadable icing.
Spread over slice while hot and decorate with extra coconut. Cut into squares once cooled a little.
