1. Preheat the oven to 165 °C / 329 °F. Prepare the baking tray and paper cups for cupcakes.
2. Whip the egg yolks with muscovado sugar and salt to a light colour and an airy texture with a whisk.
3. Gradually add the grapeseed oil to the egg yolk mixture while whipping it on medium speed. Then add the yoghurt and mashed bananas and mix gently with a silicone spatula.
4. Sift the all-purpose flour with baking powder and mix them with a whisk.
5. Add the premixed dry ingredients to the egg yolk mixture and mix it gently with a spatula.
6. Whip the egg whites on medium speed, gradually adding sugar. Whip them until medium stiff peaks.
7. Carefully fold the meringue into the egg yolk mixture using a silicone spatula.
8. Transfer the cake batter into a piping bag and pipe 40 grams of it into each paper cup. Fill no more than ¾ of the paper cup.
9. Bake for 10-12 minutes until the cupcakes rise. When ready, the toothpick, inserted in the centre of the cupcake, will come out clean and dry.
10. Transfer the cupcakes on a wire rack and leave them to cool down at room temperature.