Preheat oven to 180ºC (160ºC fan-forced). Grease 2 deep 22cm round cake pans; line bases and sides with baking paper.

Beat butter, extract and sugar in a small bowl with an electric mixer until light and fluffy. Add eggs, one at a time, beating until combined between additions. Transfer mixture to a large bowl; stir in sifted flours and cocoa and then combined buttermilk and food colouring, in 2 batches.

Combine vinegar and soda in a cup; allow to fizz then fold into cake mixture. Divide mixture between pans.

Bake cakes for about 30 minutes or until cooked when tested. Stand cakes 10 minutes before turning top-side up onto a wire rack to cool. Freeze cakes 40 minutes to make splitting and decorating easier.

Meanwhile, make cream cheese icing: beat cream cheese in a large bowl with an electric mixer until smooth. Add butter and vanilla, beat until smooth and fluffy. Gradually beat in the sifted icing sugar. Place ¾ cup of the Cream Cheese Icing in a small bowl. Tint black.

Split cold cakes in half. Place one layer on serving plate, cut-side up; spread with 2/3 cup Cream Cheese Icing. Repeat layering, finishing with remaining icing spread over top and side of cake.

Place black icing into a small piping bag fitted with a small plain tube. Pipe cobwebs over cake. Decorate with spiders and sweets, if desired. Suitable to freeze. Not suitable to microwave.