The classic Southern side dish of tender mustard greens is updated with a burst of bright green peas.
Melt butter in a large saucepan over medium heat. Add onion and garlic; cook, stirring occasionally, until translucent, about 2 minutes. Stir in greens and stock; season with salt and pepper. Cover, and cook, stirring occasionally, until greens are wilted but not completely cooked, about 8 minutes.
Stir in peas. (If you are using fresh peas, cook them 2 minutes in salted boiling water before adding to greens.) Cover, and cook, stirring occasionally, until peas are tender and bright green, about 5 minutes. Transfer to a serving dish with a slotted spoon. Serve immediately.