In a large saucepan, heat the oil over moderately high heat. Add the mustard seeds, reduce the heat to moderate and cover the pan.
When the seeds stop sputtering, remove the lid and add the ginger and green chili. Fry for three minutes, stirring occasionally.
Add the cauliflower and Knorr mix; stir well. Sprinkle the lemon juice and 1 cup of water. Cover the pan, reduce the heat to low and cook the cauliflower for 20 minutes, or until florets are tender, but not mushy/ overcooked.