Put on a large pan of water for the soba noodles. While the water gets to a boil, get started on the vegetables.
Dice the eggplant and wash the purslane. Remove the bottom of the enoki mushrooms and carefully separate them a bit.
Add the noodles to the pan and cook according to package directions until al dente. Drain and rinse.
Heat a wok with some oil and fry the eggplant in it until tender. Remove from the pan and now fry the purslane until it shrinks. This goes very quickly. Even faster than spinach. Do not overcook. Shrink and remove from the pan again. This takes barely a minute.
Finally, fry the enoki mushrooms. Again, this goes very quickly.
Because the sauce is relatively salty, I don't use salt on the noodles and vegetables.
For the sauce, take a small saucepan and in it put the miso paste and water. While stirring, bring this to a smooth sauce. Then add the chili sauce, sugar, lemon juice and the passata. Stir it well and taste to see if it is to your liking. Not every miso paste is the same. The sauce is quite salty but should be well flavored.
Put all the vegetables and mushrooms back into the wok and add the noodles. Warm briefly and serve with the sauce.