Peel, wash, and cut the potatoes into big cubes. Keep them aside.
Heat oil in a heavy bottomed pan, and splutter mustard and cumin seeds. Add garam masala and fry for a few seconds. Throw in potatoes and mix well. Transfer the potatoes to the oven straightaway, and bake for 15-20 minutes.
Alternatively, you can cook the potatoes on stove top provided you stir the potatoes occasionally to make sure they don’t stick to the bottom of the pan.