Combine the 4 tbsp (0. 5 oz / 14g) white poppy seeds, 0. 5 tbsp (0. 25 oz / 7g) black mustard seeds, and 0. 66 cups (5. 3 oz / 150g) water in a small bowl, cover, and set aside to soak for at least 4 hours or overnight.
Place the fresh bitter melon slices in a bowl and sprinkle with 1 tsp (0. 17 oz / 5g) of salt to draw out the excess bitterness.
Toss well and set aside for at least 20 minutes.
Afterward, rinse thoroughly with fresh water, drain, and pat completely dry with paper towels.
Place the soaked seeds along with their soaking water into a blender or food processor fitted with a metal blade.
Cover and process for 1 minute.
Add the ginger, chilies, and 1 tbsp (0. 1 oz / 1g) of the fresh coriander, processing until it forms a smooth paste.
Strain this paste through a fine sieve placed over a bowl containing the 0. 33 cups (2. 7 oz / 80g) of cream or half-and-half.
Stir the poppy seed mixture into the cream until well blended and set aside.
Pour your frying ghee or oil to a depth of 2 inches (5 cm) in a deep-frying pan over moderate heat.
When the temperature reaches 360°F (180°C) on a deep-frying thermometer, fry the bitter melons, potatoes, yam, radishes (or carrots), and eggplant in separate batches until they are nearly tender and golden brown.
Remove each batch with a large slotted spoon and set aside on paper towels to drain.
Remove the pan from the heat.
Heat 4 tbsp (2 oz / 60g) of ghee or an oil-butter mixture in a 4-quart (4-liter) saucepan over moderate heat.
Once hot but not smoking, add the 1 tsp (0. 1 oz / 3g) panch phoran and fry until the fenugreek seeds turn a rich golden brown.
Pour in about 0. 25 cups (2 oz / 60g) of your reserved poppy seed-cream mixture and fry, stirring constantly, until it is absorbed into the fat.
Continue adding the mixture in 0. 25-cup (2 oz / 60g) increments, stirring until all of it is incorporated. Slowly pour in the 2. 5 cups (20 oz / 600g) of water or stock and bring to a boil.
Reduce the heat to low and simmer, stirring occasionally, for 10 minutes.
Add all of the previously fried and steamed vegetables, the remaining 2 tsp (0. 33 oz / 10g) salt, and the 1 tsp (0. 1 oz / 3g) garam masala into the simmering gravy. Gently stir to combine, cover the pot, and reduce the heat to the lowest possible setting.
Cook very gently for 10 to 15 minutes to allow the flavors to meld.
Remove the pan from the heat and allow the Bitter Melon Vegetable Stew to rest for 10 minutes before serving.
Garnish with the remaining 2 tbsp (0. 2 oz / 2g) fresh coriander.
Fry in Stages: Resist the temptation to toss all the vegetables into the frying oil at once. Eggplants act like sponges and cook rapidly, while potatoes and yams need more time to crisp up and cook through.
Frying in distinct batches ensures every vegetable has the perfect texture.