125g unsalted butter, chopped, at room temperature
¾ cup caster sugar
1 teaspoon vanilla essence
2 eggs, at room temperature
1½ cups self-raising flour
½ cup milk
Liquid pink, blue and green food colourings, to tint
Edible coloured sugar, to decorate
1 cup icing sugar mixture
1 ½ - 2 tablesooons milk
Grease a 20cm round cake pan. Line base and side with baking paper.
Beat butter, sugar and vanilla in small bowl of an electric mixer until light and fluffy. Beat in eggs, one at a time, until combined. Fold in flour and milk in two batches until combined.
Divide mixture evenly among three bowls. Using food colourings, tint one pink, one blue and the remaining green.
Place alternate spoonfuls of mixtures into prepared pan. Using a flat-bladed knife, swirl through mixture twice to create a marbled effect.
Cook in a moderately slow oven (160C) for about 40 minutes, or until a skewer inserted into the centre comes out clean. Remove. Stand in pan for 10 minutes. Turn out onto a wire rack to cool.
To make icing, place icing sugar in a small bowl. Stir in enough milk to form a thick, spreadable consistency.
Spoon over top of cake. Spread evenly so it drips down the side. Sprinkle with coloured sugar. Stand at room temperature until set before serving.