Fresh purple beans, with their gorgeous hues ranging from violet to aubergine, contrasting dramatically with a green interior when cut, have enticed many a farmer's market shopper. These pretty beans have also disappointed anyone who thought that their color would remain when cooked. Alas, the purple pigment is stored in only the outer layer of the beans and disappears almost as soon as you turn the heat up under them. You're left with beans that are virtually identical to French green beans -- the regular green kind -- although some diners say the temporarily purple varieties are little sweeter and nuttier. The benefit is that you can cook purple beans using any technique intended for French green beans. Consider the color-changing magic a handy visual cue for the beans' doneness.
Preparing Fresh Purple Beans
Place the purple beans in a colander and wash them under cold, running water.
Transfer a handful of beans at a time to a chopping board and slice off the tips -- the very ends of the beans -- with a knife.
Leave the topped-and-tailed purple beans whole, slice them thinly on the diagonal, or chop them into smaller pieces. Keep the slices or pieces even in size.
Boiling Fresh Purple Beans
Fill a pan with more than enough water to cover the beans. Add a generous pinch of salt to the water and bring it to a rolling boil.
Add the prepared beans to the pan. When the water comes back to the boiling point, adjust the heat setting to keep the water boiling steadily.
Take one of the beans or pieces of bean out of the boiling water, let it cool a little, and then test it. The beans are done when they are tender but still firm. For thinly sliced beans, this will take only a minute or two; for small pieces or skinnier whole beans, it should take about 3 to 4 minutes. Thicker beans left whole will take about 6 to 7 minutes to cook.
Drain the beans in a colander, or remove them from the boiling water with tongs.
Steaming Fresh Purple Beans
Pour about an inch of cold water into a pan and bring it to a steady simmer.
Place a steamer basket into the pan. Don't let the simmering water rise above the base of the steamer.
Pile the prepared purple beans into the steamer basket and immediately cover the pan with a lid.
Test thinly sliced beans after 3 to 4 minutes, skinny beans and small pieces after 5 to 6 minutes, and whole beans after 7 to 8 minutes. If necessary, replace the lid and keep steaming the beans for another few minutes.
Remove the lid from the pan, and then remove the beans from the steamer basket with tongs.
Stir-Frying Fresh Purple Beans
Place a frying pan or wok over medium-high heat and add about 1 tablespoon of oil per pound of beans. Heat the oil for a minute or two.
Add the purple beans, sliced or whole, to the pan or wok. Stir the beans around frequently with a spatula. Keep the beans moving and don't let them sit undisturbed for more than a few seconds at a time.
Taste a bean after a minute or two after you see them change from purple to green and assess if they are done. If they are not yet ready, keep stir-frying and tasting the beans every minute or two until they are.
Transfer the cooked beans from the pan or wok to a serving dish.