Mix the flour and baking powder in a large bowl. Stir in the oats, sugar, pistachio nuts and cranberries.
Make a well in the centre and beat in the egg yolks and buttermilk to make a thick batter (it should have the consistency of thick cream). In a separate bowl, whisk the egg whites until stiff but not dry and fold into the batter.
Heat a griddle pan or large heavy-based non-stick frying pan over a moderate heat. Add a tiny drop of oil to the hot pan. When the pan is hot, drop a heaped dessertspoon of the batter into the pan, flatten slightly with the back of the spoon, so that the pancakes are about 10cm in diameter and about 0.5cm thick.
Cook for about 2 minutes or until bubbles start to break on the surface and pancakes are firm enough to flip. Flip and cook for 1 to 2 minutes more, until they feel springy when prodded. Transfer to a warm oven while you cook the rest, adding more oil as necessary. Serve with Greek yoghurt and some fresh summer berries.
If you have trouble finding buttermilk you can use 150ml of plain yoghurt mixed with 130ml semi-skimmed milk instead.