Preheat the oven to 350 degrees F/180 degrees C/Gas 4 and line an 18-ounce/500-gram loaf tin with baking paper. In a bowl, mix together the flour, goat's cheese, prunes, pistachios and baking powder. In a separate bowl, whisk the eggs until fluffy and pale in colour. Then gradually whisk in the oil, milk and yoghurt. Add the salt and black pepper. Fold the flour mixture into the whisked eggs. Try not to over-beat as this will make the end result tough (it's better to under-mix). Pour the batter into the prepared tin. Bake until a metal skewer inserted in the centre of the cake comes out clean, 30 to 40 minutes. Leave to cool in the tin.