Here is the recipe
Ingredients :-

1. Bittergourd -1
2. Potato -1
3. Ambado/hog plum – 2
4. Red chillies – 6-8 nos
5. Coriander seeds – 2 tsp
6. Urad dal – 1 tsp
7. Methi – 1/2 tsp.
8. Salt to taste

Seasoning:-

1. Mustard – 1 tsp
2. Curry leaves – 1 sprig
3. Oil – 2tsp

Method:-

• Chop karathey and Batato  and ambados into 1/2 “inch length.Add enough water and salt to the vegetables and allow them to cook till soft.Meanwhile roast coriander,urad dal and methi with a tsp of oil.When cool grind it along with red chillies.
• When the vegetables are cooked add this paste to it and boil well.
• Prepare seasoning with mustard and curry leaves in oil.Pour this over the boiled curry.Its ready to serve.

Note:
1.If hog plum is not available can use bimbli/bimbul/karmbal or tamarind pulp.
2.Can use two types of chillies (spicy n non spicy) too.They need not be roasted in oil.
3.If you want to use it for 3-4 days,then it needs to be boiled twice a day at morning and night.
4. You can apply salt to bitter gourd to remove the bitterness and after squeezing can boil with the potato and follow the rest of the procedure.