Preheat oven to 175C. Whisk eggs and sugar in an electric mixer until pale and fluffy. Fold in flour, then remaining ingredients. Divide mixture among eight 125ml metal dariole moulds on an oven tray and bake until cakes are puffed, golden and spring back when lightly touched (30-40 minutes). Cool slightly in moulds (5 minutes), then turn out onto a wire rack to cool completely.
Meanwhile, for orange icing, whisk ingredients in a bowl until smooth. Drizzle icing over cool cakes, then leave to set (1 hour). Cakes will keep stored in an airtight container in a cool, dry, dark place for 3-4 days.