As for serving suggestions for your homemade kahlua . . .
Straight up, mix with milk or cream, mix with coke, mix with coffee, 3 parts vodka to 2 parts kahlua (or 5 parts vodka to 2 parts kahlua according to the IBA) makes a black Russian, a bit of milk or cream in your black Russian makes a white Russian . . .
@hungrychristel got the idea from the Good Eats episode on greens. Especially if it's something that winds up changing the color of the water you cooked it in you've probably got some of the flavors of the vegetable in the cooking liquid. As well as anything you tossed in to flavor the finished vegetable. Just be careful if it's something strong like mustard greens that it doesn't overwhelm what you use it in.
@KenG A lot of the sites I've seen are actually saying don't use whey. It has the wrong bacteria for fermenting vegetables and produces poor results.
The problem of water soluble nutrients is easily solved by saving and re-using the liquid the vegetables were boiled in - or simply drinking it. For example after I boil a big pot of greens I'll retain the liquid and use it to stew lentils.
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