1.Preheat oven to 180°C/350°F. Grease deep 20cm (8 inch) square cake pan; line with baking paper.
2.Beat butter, extract and sugar in small bowl with electric mixer until light and fluffy. Beat in eggs, one at a time.
3.Transfer mixture to large bowl; stir in coconut, sifted flour, sour cream and milk, in two batches.
4.Spread mixture into pan; bake about 40 minutes. Stand cake in pan 5 minutes before turning, top-side up, onto wire rack to cool.
5.Meanwhile, make coconut ice frosting by sifting icing sugar into medium bowl; stir in coconut and egg white. Place half the mixture in small bowl; tint lightly with pink colouring. Drop alternate spoonfuls of white and pink frosting onto cold cake; spread over top of cake, swirling to create a marbled effect.
Store in an airtight container, at room temperature, for up to one week. Un-iced cake can be frozen for up to three months.Note