Separate the eggs into 2 bowls, egg yolks in one and egg whites in another. Put the butter in a heatproof bowl and heat in the microwave for 30 seconds until melted. Add the milk and pour the mixture over the egg yolks, stirring well.
Put the flour, baking powder and 1 tablespoon of the sugar in a large bowl. Add the milk mixture and whisk well to make a smooth batter. Stir in the blueberries.
Whisk the egg whites until they form firm peaks. Using a large metal spoon, gently fold the whites into the batter until well mixed.
Heat a little oil in a large frying pan for 1 minute. Add a dessertspoonful of the batter to one side of the pan so it spreads to make a little cake. Add 2–3 more spoonfuls, depending on the size of the pan, so the pancakes can cook without touching. When the pancakes are golden on the underside (check by lifting with a palette knife or fish slice), flip them over and cook again until golden. Remove the pancakes from the pan and transfer to a serving plate, then keep them warm while you cook the remainder.
Sprinkle with the remaining sugar and serve.