Microwave potatoes 3-4 minutes or until soft. While they are cooking, chop onion and saute in a large skillet until translucent (Onion can be sauteed in oil, water, or juice from mustard greens). When potatoes are cooked, quarter them and cut into slices about 1/2 thick. Throw the potatoes and drained mustard greens in the skillet with the onions, and cook on low to medium heat for about 10 minutes.
Mixture can be served with a dash of balsamic vinegar, salt and pepper, or just about any spices.
This is a surprisingly yummy combination - even my cats like it!