Finely chop the onions and blanch them with a bit of oil in a medium-sized saucepan for about 2 minutes.
Peel and chop the potatoes into bite-sized chunks and the kohlrabies into sticks.
Add water and vegetable stock cube to the saucepan and bring to boil.
Layer the potatoes and kohlrabi in 2-3 bamboo steam baskets on top. It is also possible to simply boil them instead, but steaming will preserve more nutrients.
Sprinkle a little salt over the potatoes and kohlrabi and steam them at high heat for about 20 min.
Meantime grease an oven prove dish and layer the steamed vegetable in it once finished.
Make sure to keep the vegetable stock you might need to add a little water to gain a total amount of liquid of approximately 1 2/3 cups.
Preheat the oven to 425 °F/220 °C.
Add the soy cream, butter or vegetable spread and flour to the vegetable stock and boil for 4 minutes.
Roughly chop the basil leaves, and add them to the sauce, mix carefully with an immersion blender.
Salt, pepper, nutmeg and lemon juice can be added to taste.
Pour the basil sauce over the steamed vegetable in your oven prove dish and cover with your choice of grated cheese.