Preheat the oven to 180C/350F/gas mark 4
Use a 19cm x 29cm lamington tin.
Line the base of the lamington tin with greaseproof paper. Grease the paper. Stir coconut constantly over heat in heavy frying pan until light golden brown. Remove from pan to cool. Cream the butter and sugar in small bowl until light and fluffy, add the sour cream and golden syrup and mix well. Transfer the mixture to large bowl, stir in the toasted coconut, half the sifted flour and half the milk, then stir in remaining flour and milk. Spread mixture into prepared tin.
Bake in for about 35 minutes. Allow to stand for 5 minutes before turning on to wire rack to cool. Spread the cold cake with icing, sprinkling with extra coconut if desired.
Caramel Icing. Melt butter in saucepan, add sugar, stir constantly over heat without boiling for about 2 minutes. Stir in milk then gradually stir in sifted icing sugar, stir until smooth.