Thaw frozen salmon. In the meantime, wash the potatoes and cook them unpeeled for about 20 minutes. Quench the draining immediately, peel and cut into slices.
Rinse the salmon fillet with cold water, pat dry and dice. Cut the chicory into wide strips and layer them in a baking dish with the potatoes and salmon.
Season everything vigorously with salt and pepper. Whisk the mustard with the cream and spread over the ingredients in the baking dish.
Coarsely grate the cheese and sprinkle over it. Bake on the middle rail of the 200 degree oven for about 35 minutes.