Pour fish into a sieve and drain well. Peel garlic and chop finely. Put half of the capers, garlic, tuna and salad cream into a tall mixing bowl and mix well with the whisks of the hand mixer.
Season to taste with salt and pepper. Finely puree the cream with a blender. Cut the gherkins into fine slices. Wash parsley, dab dry and chop finely. Pour into a piping bag with a large star-shaped spout.
Cover the crackers with some salad as desired. Spray a tuff of the cream on each cracker. Serve garnished with remaining capers, parsley and gherkins.