Place potatoes in a saucepan, cover with water, add salt, and bring to a boil.

Simmer until potatoes are par-cooked (soft but not mushy).

Strain potatoes, reserving some boiled water.

Grind all ingredients under 'For the Vindaloo paste' into a fine paste.

Heat oil in a kadai, add mustard seeds and curry leaves.

Add vindaloo paste and saute until the raw smell disappears and oil separates.

Add reserved potato water, boiled potatoes, and salt to taste.

Cook until the curry thickens, stirring occasionally (10-12 minutes).

Sprinkle sugar and stir.

Add additional curry leaves and serve hot.