We find the best way to treat milkweed is to cook it lightly, just blanch it until the leaves have wilted (about 2-5 minutes) and serve with a light dressing. Serve it in place of another freshly flavored green vegetable.
Although I often eat common milkweed raw as I am harvesting it and cooking it I should advise you to eat it cooked since it is reported to contain small amounts of digoxin which is be poisonous to humans when eaten in large quantities. Digoxin is considered to be water soluble and blanching and discarding the water should remove the toxin. I have not encountered any accounts of human poisoning by common milkweed but it is always best to err on the side of caution so a brief cooking will render your milkweed safe to enjoy.