Verdigris on copper-bottomed pan I have a small stainless steel pan with a copper bottom. The diameter is around 4in or 10cm, so it is really small. I use it exclusively for tempering or what is known in India as tadka. That is, I heat a couple of spoonfuls of ghee, add the necessary spices (mustard seeds, cumin seeds, curry leaves, chili peppers, asafœtida, whatever the recipe calls for), then add the tempering to the main dish, usually lentils or a stew.
Since the pan is tiny, my usual method of adding the tempering is just to dunk the entire pan into the larger pan that has the main dish. Then I scoop up some of the main dish with the smaller pan, swirl it around to gather any fat or spices left in the pan, and pour this back into the main dish, repeating the process a couple of times.
The last time I tried this (a couple days ago), I was horrified to notice that the copper bottom of the pan was beginning to develop verdigris. Here is a picture:

I'm obviously concerned about this. I have three questions:

Should I give up the habit of dunking this little pan into the larger pan? Will the verdigris get into the food and make it dangerous to eat?
Is there any way I can get the verdigris off the bottom of the pan?
Assuming there is, what can I do to prevent a recurrence? For example, I usually put this pan in the dishwasher. Should I be washing it by hand instead?

I want to avoid replacing the pan if possible. It is very useful and I don't know where I'd find a similar pan; the pan was gifted to me many years ago by someone who in turn had had it for some time before she gave it to me.
Corrosion like that can be scrubbed off with copper polish (or, in a pinch, with salt and vinegar). The result will be bright copper, which will quickly tarnish and darken through regular use. The pan is absolutely not ruined. As with other solid metal cookware, if it isn’t literally broken in pieces then it can be scoured into a like-new state. That pan likely has centuries of use left in it.
Dunking the pan like that doesn’t sound like a problem. The upper surface of the pan comes into contact with food, after all; no reason the bottom surface can’t. I think it’s a clever technique.
The dishwasher is your real enemy here. It’ll strip away the patina and bring the surface into contact with some pretty harsh detergents, leading to that sort of corrosion. Copper should be hand-washed.