Slit the bitter gourds lengthways and de-seed, then rub them all over with salt. Place on a large tilting tray (roasting pan) and set aside for 1 hour.
For the filling, put the ginger in a mortar and pound with a pestle or process in a blender to make a paste. Set aside.
To blanch the bitter gourds, heat enough water to cover the gourds in a large pan, season with salt, and add the ginger and garlic pastes and turmeric. Bring to the boil, then add the bitter gourds and blanch for 3-4 minutes, or until soft. Drain and set aside.
To make the filling, put the peanuts, sesame seeds, cumin seeds, and onion in a blender or food processor pour in 4 tablespoons water, and process to make a paste. Transfer to a large bowl and add the paneer, ginger, green chillies, coriander, jaggery or sugar, tamarind extract, and garam masala. Season with salt and mix well.
Preheat the oven to 140'C / 275°F / Gas Mark 1 and oil a large roasting tray (pan).
To make the tempering, heat the oil in a frying pan (skillet) over medium heat, add the cumin, mustard, fenugreek seeds, and stir-fry for about 1 minute, or until they start to splutter. Remove and pour over the filling, then mix well and divide the mixture into equal portions, one for each gourd.
Stuff the bitter gourds with the filling and arrange in the prepared roasting tray with the open side on top. Cover with foil, punch a couple of holes in the foil, punch a couple of holes in the foil and cook in the hot oven for 30 minutes, basting with oil or ghee at regular intervals. serve hot.