For the pancakes, place the flours, eggs, milk, salt and horseradish sauce into a food processor and blend until smooth (or whisk by hand with a balloon whisk.)
Place a large heavy-based frying pan over a medium heat and lightly butter the pan using kitchen paper. When the pan is hot, drop one dessertspoon of batter into the pan and repeat three times to make four small pancakes.
After 1-2 minutes, when you see bubbles forming on the surface of each pancake, flip them over and cook for a further minutes, or until no batter oozes out when the pancake is lightly pressed with your fingers.
Remove the pancakes to a wire rack and cover loosely with a clean tea towel. Continue making the pancakes until all the batter is used up.
For the topping, mix the crème fraîche with the horseradish in a bowl and season, to taste, with salt and freshly ground black pepper.
To serve, place the pancakes onto serving plates. Top with a spoonful of the horseradish cream, some slices of salmon and sprigs of dill.