In Chinese cuisine, "gwa" - usually translated as squash or melon - covers a wide variety of vegetables and fruits such as watermelon, fuzzy melon, winter melon, Chinese okra and bitter squash. In traditional Chinese medicine, these ingredients are considered cooling, so are eaten when it's hot outside (although many of them are also delicious when it's cold).
Bitter melon lives up to its name, but it's a pleasant bitterness that is muted when cooked with other ingredients. Some specimens are more bitter than others, and if you get one that's especially bitter, cut it in half, scrape out and discard the seeds and pith, then sprinkle salt over the interior. Leave for about 10 minutes, then rinse it - the salt will draw out some of the bitterness.
When buying the pork spare ribs, have the butcher cut them through the bones into 1.5cm (⅔ in) pieces. If you try to cut them at home, it requires a very sturdy cleaver and a thick cutting board.
Put the ribs in a bowl and add the soy sauce, rice wine, salt, pepper, sugar, cornstarch and 10ml (2tsp) of cooking oil. Mix thoroughly and leave to marinate at room temperature for about 30 minutes.
Put the black beans in a small bowl, add 30ml (2tbsp) of warm water and leave for about 30 minutes, then lightly mash them with the back of a spoon.
Cut the garlic cloves in half and thinly slice the shallots. Cut the bitter melon in half lengthwise then scrape out and discard the seeds and the pith. Cut the melon on the diagonal into slices about 6mm (¼in) thick.
Heat about 15ml (1tbsp) of cooking oil in a wok placed over a high flame. Add the bitter melon melon and stir-fry for about a minute (this sets the colour, keeping it bright green). Remove the melon from the wok.
Heat 20ml (4tsp) of cooking oil in the wok (no need to wash it) and place it over a high flame. When the oil is very hot, add the garlic and shallot and stir-fry for about 15 seconds.
Add the pork ribs and cook until the pieces are no longer pink, stirring often.
Add the black beans and the soaking liquid. Stir briefly, then scrape the ingredients into the centre of the wok. Lower the heat, cover the wok with the lid and simmer, stirring occasionally, until the meat is cooked through. If the mixture gets too dry, stir in some hot water.
When the meat is tender, add the bitter melon back to the wok and stir well.
Turn the flame to medium-high. Add a little more water to the wok, if needed, then simmer the ingredients, stirring often, until the bitter melon is done to your liking. The sauce should lightly coat the ingredients.
Taste the sauce and correct the seasonings, if necessary. Stir in the sesame oil then transfer the mixture to a dish and serve.