Bring 250 ml water and salt to the boil. Remove the pot from the stove and add milk. Stir in puree flakes. Peel horseradish and grate finely. Stir into the puree. Put 2 salmon slices next to each other.
Pour the puree on top, roll it up and lay it next to each other in a greased casserole dish. Sprinkle with crème légère and bake in a preheated oven (electric range: 200 °C/ convection oven: 175 °C/ gas: level 3) for approx. 15 minutes.
Garnish with dill.