For the batter, separate the eggs.
Mix the flour and buckwheat flour in a bowl. Mix in the yeast and sugar.
Stir the milk, melted butter and egg yolks into the flour until smooth.
Cover and leave to stand in a warm place for 30 minutes.
Whisk the egg whites until stiff. Add the salt. Fold the beaten egg whites into the batter.
Melt some butter in a pan. Add 2-3 separate tbsp of batter and fry for 2 minutes until golden underneath.
Turn the pancakes and fry on the other side until golden brown. Fry the remaining batter in the same way in hot butter. Keep the finished pancakes warm in a low oven. Serve the pancakes with a little crème fraîche and caviar.