200g/7oz plain flour
1 tsp baking powder
1 tsp bicarbonate of soda
1 tbsp caster sugar
录 tsp salt
25g/1oz unsalted butter, melted (or vegetable oil)
150ml/5fl oz kefir (or yoghurt or buttermilk)
2 large free-range eggs, separated
100ml/3陆fl oz full-fat milk