This is a variation on the Lemon Yogurt Cake recipe which wasn't so successful the last time I tried it with added blueberries and apple. I wondered then if the problem wasn't the extra rich yogurt I was using, with around 10% fat levels, so this time I used 100g buttermilk, 100g of the same yogurt as last time and 50g semi-skimmed milk to make up the volume needed (250mls). I also used only 100g oil, as I realised that weighing out 125g was probably giving me more than the 125mls called for in the recipe. This time I baked the cake in a 8" (20cm) round tin, and it cooked in 55 minutes.
The result was a much more acceptable texture - more open and cake-like than before, and quite moist, although light too. Not perfect, and there were a few random large air bubbles which I'd prefer not to see, but much better than before.
The method is simple - sift the flour, baking powder and salt together. I added the orange zest to the flour mix after sifting and whisked it in. Whisk the sugar, yogurt, eggs, vanilla and oil together until smooth, then fold in the flour mixture. Finally fold in any solid additions - in this case the chocolate chunks.
Bake at 180C, until a test probe comes out clean - around 50 minutes. Cool for about 20 minutes in the tin, then turn out onto a wire rack until completely cold.
I look forward to trying other flavour variations of this cake in future, and maybe even trying fresh fruit again, now that the 'yogurt question' seems to be answered.