Preheat the oven to 160°C conventional or 140ºC fan-forced. Grease a 21cm round springform tin (with high sides) and line base with baking paper.
Beat Chelsea White Sugar (or Chelsea Organic Raw Sugar), melted butter and eggs until pale and creamy. Add the mashed bananas and beat well.
Heat the milk in the microwave until nearly boiling (approximately 1 minute). Mix in the baking soda then stir into the banana mixture.
Add the yoghurt, flour and baking powder. Mix well and pour into the prepared cake tin. Bake for 45-50 minutes until the cake is cooked in the middle and just pulling away from the edges of the tin (insert a skewer into the centre and if it comes out clean it is cooked). Cool in tin for 5 minutes then release the sides and cool on a wire rack. When cold, swirl with icing.
In a bowl mix the Chelsea Icing Sugar and lemon juice. Add butter and beat until light and fluffy. Add a little hot water for a softer consistency if required.