Heat the oven to 170ºC. Grease and base line a 10-inch cake tin.

Mix together the flour, sugar, baking powder and a pinch of salt in a mixing bowl. In a separate bowl, whisk together all the wet ingredients, stirring well until smooth and well blended. Combine the dry ingredients and fold in gently.

Whisk the egg whites to soft peaks. Add the cream of tartar, beating well until stiff. Fold a third of the egg whites into the egg yolk mixture to loosen it. Then gently fold in the remaining egg whites.

Pour into the prepared cake tin. Bake for about 35 minutes until golden and firm to the touch. Leave to cool in the tin and then turn out into a serving plate.

Meanwhile, mix all the custard topping ingredients together in a small saucepan, stirring well to combine. Make your frosting a bit runny but not too runny, a frosting that spreadable enough.