125g butter, softened
3 eggs, separated
150g caster sugar
1 tsp vanilla extract
1/2 cup cold mashed sweet potato
190g self-raising flour, sifted
1/3 cup yoghurt
zest of 1 lemon
3 tbsp cocoa powder
- Grease and line a 14cm x 21cm loaf pan.
- Preheat oven to 160 degrees C.
- Cream butter and sugar until light and fluffy. Beat in egg yolks, lemon zest and vanilla extract until combined.
- Beat egg whites until firm peaks form.
- Stir in mashed sweet potato with 1/3 of the sifted flour and half of the yoghurt. Then stir in remaining flour and yoghurt.
- Fold in beaten egg whites.
- Spoon 1/3 of the mixture into a separate bowl and stir in cocoa powder. Combine well.
- Place the cake mixtures into the prepared pan by alternating layers of the vanilla batter with the chocolate batter.
- Bake for about 40 minutes or until cake is done.