Sift the flour and bicarbonate of soda into a bowl. Make a well in the centre and whisk in the beaten eggs. Gradually whisk in buttermilk, melted butter and sugar.
Heat a heavy-based non-stick frying pan (about 20-22cm in diameter) over moderate heat. Use a piece of kitchen paper to grease the pan with a little sunflower oil.
Drop tablespoonfuls of the batter into the pan and cook until bubbles form on the surface of the pancake and the underside starts to turn golden brown. Use a palette knife to flip the pancake and cook the other side until golden brown, about 1 or 2 minutes. Turn out of the pan and repeat with remaining batter, greasing the pan between pancakes if necessary.
Stack the pancakes on top of each other to keep warm.