1.Preheat oven to 180°C (160°C fan-forced). Grease two 12-hole (1-tablespoon/20ml) shallow round-based patty pans.
2.Make cake according to directions on packet. Drop 3 level teaspoons of mixture into each pan hole; bake about 10 minutes. Stand cakes in pans 5 minutes; turn onto wire rack to cool.
3.To make butter cream, beat butter in a small bowl with an electric mixer. Gradually beat in half the icing sugar and beat until as white as possible. Add milk and continue beating, then add remaining icing sugar. Beat until a smooth, spreadable consistency.
4.Divide butter cream into three small bowls; tint each bowl with one of the suggested colours: red, blue and yellow.
5.Brush warm jam over rounded bottoms of cakes. On a surface dusted with sifted icing sugar, knead the ready-made icing until smooth. Divide icing into three equal portions; tint each portion with one of the suggested colours: red, yellow and blue. Roll each portion into a 3mm thickness. Cut eight 6cm rounds from each portion.
6.Using picture as a guide, and using hands dusted with icing sugar, gently mould, shape and smooth the icing over the bottom of one cake at a time; fold a little icing over flat edge to cover edges. Repeat with remaining cakes and icing.
7.Stand cakes, rounded-side up, on a fine wire rack for about 30 minutes or until the icing is firm. Sandwich cakes with a little butter cream. Wrap lengths of bootlace around each yo-yo.