Sweet potato cupcakes with burnt sugar frosting

Oh my.

These were supposed to be an experiment, a way of using up a surplus of sweet potatoes that I have somehow accumulated. They were not intended to be as moreish and tasty as they are.

Fresh from the oven these cupcakes have a delicate crust and moist, fluffy interior. I baked them at midnight and somehow managed to polish off two before falling asleep. There's really no need to add the burnt sugar frosting, but because it's so finger-lickin' delicious, I did.

Makes a dozen cupcakes

75g room temperature butter
190g caster sugar
3 medium eggs, separated
½ cup of cold, steamed (or microwaved) sweet potato, well stirred
2 tbsp plain yoghurt
1 tsp vanilla extract
130g plain flour
1 tsp baking powder
a pinch of salt
½ tsp ground cinnamon

~for the frosting
150ml double cream
3 tbsp cream cheese
2 tbsp caster sugar
2 tsp water

1) Cream together the butter and sugar until light and creamy, then beat in the egg yolks, sweet potato, yoghurt and vanilla. Sieve in the flour, salt, baking powder and cinnamon and fold into the batter.

2) Now whisk the egg whites until they form stiff peaks, then fold into the cake mixture. Spoon into 12 muffin paper cases, and bake for 18-20 minutes at 375f/ 190c/ gas mark 5, until a toothpick inserted into the cakes comes out clean.

3) Allow the cakes to cool. Meanwhile, you can make the frosting: beat the cream cheese in a bowl until really smooth, then place the sugar in a small pan. Heat without stirring until it has formed a dark caramel syrup, then carefully add the water and shake the pan a bit to encourage it all to melt together.  Pour onto the cream cheese and beat in thoroughly. Add the cream and beat the mixture until it thickens to the consistency of veyr soft butter, then use to spread over the cakes.