Use the vegetable peeler to peel the Jerusalem artichokes. Cut them in even pieces and add them to the cooking pot. Pour in some water, the lemon juice and the vegetable stock cube.
Take the outer layer of the onion. Chop the onion into small cubes and add it to the cooking pot as well.
Clean the Swiss chard and cut into thin strips.
Cooking
Cook the Jerusalem Artichokes for about 5-10 minutes. The cooking time depends on the size of the vegetables.
When cooked through, drain the Jerusalem Artichokes and onions. Mash it with salt, pepper, the swiss chard and creme fraiche.
Crumble the feta cheese on top of the mash and top with roughly chopped hazelnuts. Serve with spicy mustard!