6 cups fresh butter beans or three 10-ounce boxes frozen baby lima beans
1/2 cup extra-virgin olive oil
1/4 cup plus 2 tablespoons fresh lime juice
1/4 cup plus 2 tablespoons buttermilk
Salt and freshly ground black pepper
1 cup chopped mint
Bring a large saucepan of salted water to a boil. Add the butter beans and cook until they are tender, 8 to 10 minutes. Drain and rinse the beans under cold running water. Drain well and pat the beans dry.
In a large bowl, whisk the olive oil with the lime juice and buttermilk; season the dressing with salt and pepper. Add the beans, cover and refrigerate for 2 hours. Fold in the mint before serving.
The butter bean salad can be refrigerated for up to 2 days. Add the chopped mint just before serving.