Blanch the thoroughly washed cabbage, freed from the stems, in boiling salted water, drain and cut coarsely or finely.
Melt the fat and roast the diced onions in it until light yellow. Then add the cabbage and heat for a short time. Add the water, a little salt and the oat flakes. Steam the cabbage over a low heat for about 1-1 1/2 hours until it is cooked and season with salt.
Tip: Adding 1-2 tablespoons of mustard seeds makes the kale more piquant.