I wonder if we can get Sorrel, I've never looked. Let's assume we can. I'd experiment with quantities until it tasted right, and would use wine and water to wet it rather than vinegar, since that would mask the taste. I think, and a vegetarian one at that. So, use your favorite quiche recipe and stick in a variety of period vegetables.
Spinach has been done, so leave it out.
Onions are good. Maybe broccoli, I think it's period but don't quote me. Hey, here's a tarte recipe that calls for borage, maybe try that. Take borage floures and perboyle them tender, then strayne them wyth the yolckes of three or four egges, and swete curds, or els take three or foure apples, and perboyle wythal and strayne them with swete butter and a lyttle mace and so bake it. So take the borage and parboil it.