Sarson da saag (Sarson ka saag, in Hindi, Urdu) is a popular vegetable dish in Punjab region of India and Pakistan made from mustard leaves (sarson) and spices. However, it is also popular in other neighboring states of Haryana and Rajasthan. It cannot be said confidently that it originated in the Punjab region.
It is regarded as the traditional way of making saag, and is traditionally served with makki di roti, which literally means (unraised) corn bread. It can be topped with either butter (unprocessed white or processed yellow butter) or more traditionally with ghee(clarified butter). Some spinach (called palak in Punjabi) can be added for added colour and thickening the dish, even if this could alter the taste. -Source: Wikipedia
Note
* Makkai ki Roti and Sarson ka Saag are made for each other.