1Heat the oven to 250°F. Place the buckwheat flour, plain flour, baking powder, sugar and salt in a bowl and stir to combine. Place the egg yolks and buttermilk in another bowl and stir well to combine. Add the buttermilk mixture to the flour and mix lightly until just combined. A few lumps are fine, so do not over mix. Place the egg whites in a clean, dry stainless steel bowl and whisk until stiff peaks form. Using a large metal spoon, fold the egg whites through the batter in two batches.
2Heat a large non-stick frying pan over a medium heat and brush a small portion of butter over the base. For each pancake, ladle 4 tablespoons of batter into the pan and sprinkle with a heaped tablespoon of blueberries. Cook for about 2 minutes, or until bubbles appear on the surface of the pancake. Turn the pancakes over and cook for another minute. Transfer to a plate and keep warm in the oven while you make the remaining pancakes.
3Serve the pancakes in stacks of three with the yogurt, mango and a jug of maple syrup.