Many cooks think chives are the best tasting member of the onion family. They go with loads more than summer salads and are attractive to look at too.
Keep in mind
The taste is mild, halfway between a herb and onion. It tends to disappear in a stew.
If you grow your own: replace it from time to time, chives lose flavor over time.
How to cook chives
You don’t really. You add them to the dish at a late stage (or earlier if it’s served cold) as an onion, a spice and a garnish all at once.
Make sauces, e.g. a beautiful green vinaigrette or some kind of emulsion. Here too the flavor will vanish if cooked for a long time at a high temperature. Add lemon or vinegar so the color doesn’t fade.
Chop and garnish: Chives are decorative when finely chopped, less finely chopped or as long straws. Any mise en place worth its salt should include chopped chives.
To add flavor and as a garnish on top of a cold sauce of sour cream, yoghurt or similar.