Heat oven to 190C/fan 170C/gas 5. Line 18 holes of a 2 x 12-hole bun tins with paper cake cases. Melt butter and cool for 5 mins, tip into a large bowl with all the cake ingredients, then beat together for 1-2 mins until smooth.
Spoon the cake mixture into the cake cases, filling them three-quarters full (a heaped tablespoon is about right). Bake for 15-18 mins until lightly browned and firm to the touch. Cool on a wire rack.
To make the icing, put the egg white and orange juice into a heatproof bowl, sift in the icing sugar, then set over a pan of simmering water. Using an electric hand whisk, whisk the icing for 7 mins until it is glossy and stands in soft peaks. Remove from the heat, then whisk for a further 2 mins until it is slightly cooled.
Thinly slice the fruit jellies. Spoon the icing onto the cakes, swirling it with a knife, then decorate with slices of jelly fruits and a few silver balls. Leave to set. The cakes will keep for up to 3 days in the cake tin.