Combine sifted flour with baking soda and baking powder. In a separate bowl, lightly beat egg and add milk. Make a well in the centre of the flour mixture and pour in egg and milk. Stir with a whisk until smooth and thick.
Spoon a tablespoon of mixture into a lightly greased, non-stick frying pan. Cook over a medium heat for 3 minutes, until bubbles appear on the surface. Turn and cook for 1 minute. Repeat with remaining batter and set aside to cool completely.
Combine sour cream, mustard and horseradish. Stir in chives and season with pepper. Spoon onto cooled pancakes and top with slices of smoked salmon. Garnish with extra chives and serve.