Halve the avocado, remove the core and peel the flesh. Cut the flesh into fine cubes. Cut smoked salmon into fine cubes. Peel and finely dice shallots. Wash dill, shake dry, pluck little flags from the stems.
Chop the flags finely, except for something to decorate.
Mix avocado, salmon, half of the shallots and dill, season with salt and pepper. Divide the tartar into 4 dessert rings (8 cm Ø) and press lightly.
Mix the vinegar and the rest of the shallots cubes. Add oil and season with salt and pepper. Wash salad, spin dry and mix with vinaigrette.
Divide the salad into four plates. Place the tartar in the middle and carefully remove the rings. Add horseradish and decorate with dill.