Boil the beets until soft in lightly salted water. Let them cool completely. Peel and slice the beet as thin as possible (I recommend using mandolin). This can be done one day before serving.
Continue with the salt roasted walnuts. Turn oven on 180°C (360 F). Bring salt and water to boil. Add the walnuts and simmer for 5 minutes. Place on a baking sheet and roast in the oven for about 12 minutes. Let them cool.
Mix all the ingredients for the Goat Cheese Cream. Place in a piping bag.
Mix all ingredients for the Lemon Vinaigrette.
Arrange the starter. Overlap slices of beets on 4 large plates, dividing equally. Add arugula, chopped walnuts and goat cheese cream. Drizzle with lemon vinaigrette and sea salt.