No-bake chocolate-banana cake with no added sugar: Olympic canoeist Saúl Craviotto's four-ingredient recipe

Olympic canoeist Saúl Craviotto has a recipe for a situation everyone knows: it's evening, you want something sweet, and all the kitchen has is bananas that are starting to go black. His chocolate cake needs no oven, has no added sugar and only four ingredients. "Save the recipe, it'll rescue you from more than one sugar craving," he says.

Ingredients: about 100 grams of dark chocolate, two ripe bananas, pure cocoa for dusting and chopped pistachios.

Method: melt the chocolate in the microwave, mash the bananas and mix them with the melted chocolate. Pour the mixture into a springform tin and leave it in the fridge until it sets. Once out of the tin, dust it with cocoa and cover it with chopped pistachios. The result is creamy and sweet, with a crunchy top layer.

The trick is in the banana. The riper it is, the sweeter it is - and the less sugar you need. That logic applies more widely too: ripe fruit instead of sugar, dark chocolate with a high cocoa percentage, nuts, wholegrain oats or plain yoghurt. One warning: sweeteners aren't the same as sugar, neither in strength nor in how they behave in a batter, so don't swap one for the other by guesswork.

When an athlete with Olympic medals says dessert doesn't have to be a sin, it's worth a try. Five minutes of work, a little patience while it chills - and the dessert is ready without a single spoonful of added sugar.