In a moderately heated pan add oil, add onion seeds and allow to sizzle. Then add finely chopped potatoes + salt + turmeric + chili powder and stir fry for 4-5 minutes. Now sprinkle 3 tbsp water, simmer and cook till potatoes turn soft. The filling is ready and let it cool.

Take bread slices, apply butter on both sides, put potato filling, and cover it with another slice keeping the buttered side out, and press gently.

Now toast either on tawa or sandwich maker, it takes just a few minutes to toast. The potato sandwich is done. Cut diagonally.

Now potato sandwich is ready to Serve.