Cut the salmon fillet into small cubes.
Peel and finely chop the shallots.
Wash the dill, shake dry and chop finely.
Place the salmon, shallots and dill in a bowl. Mix with the white wine vinegar, lemon juice, sour cream and horseradish cream, and season with salt and pepper. Cover and chill in the fridge.
Peel the celery and grate coarsely. Lightly salt and leave to stand for 10 minutes.
Place the celery in a clean tea towel, and squeeze out the liquid into a bowl.
Peel the apples, quarter, core and coarsely grate then press out the liquid with the tea towel.
Mix the grated celery and apple with the egg and flour. Season with salt and pepper.
Place heaps of the mixture into a non-stick pan with 2-3 tbsp hot oil, flatten them with a spatula and fry for 2-3 minutes until golden brown. Turn and fry for another 2-3 minutes until golden brown. Continue until all the mixture is used up. Drain on kitchen paper and keep the cooked fritters warm in a low oven. Arrange the cooked fritters and salmon tartare on plates. Garnish with dill and serve with lemon wedges.