Wow, that is a good question. I am also zone 7a but doubtful that our weather is exactly like yours. Some perennial veggies here are asparagus, rhubarb, garlic, Jerusalem artichokes, some leeks, bronze fennel, shallots, sorrel, horseradish (herb). There is a winter hardy kale that grows in Europe that I'm trying to locate.
Some others I've heard about but not grown so can't vouch for are: lovage, Good King Henry greens, salsify, sea kale (Crambe maritima).
You might also post this question in the Vegetables Forum. But I hope we get some more responses here.