When you see bok choy you might think stir-fry, but we here treat it like a hearty green, wilting it and softening it in bacon drippings. Then we add big, creamy butter beans and a splash of vinegar. Serve it right out of the pan or at warm room temperature. And if you have it on hand...stir fresh corn kernels in with the beans.
Add the bacon to a large skillet and cook over medium heat, stirring occasionally, until brown and crisp, about 6 minutes. While the bacon cooks, cut the stems from the bok choy into 1-inch pieces and the leafy tops into 3-inch pieces.
Add the onion to the bacon and cook, stirring, until softened slightly, 4 to 5 minutes. Toss in the beans and stir until heated through, about 2 minutes. Transfer the vegetables with a slotted spoon to a bowl, leaving the fat in the pan.
Add the bok choy stems to the pan, increase the heat to medium-high and cook, stirring, until slightly softened, about 2 minutes. Add the bok choy leaves and cook, stirring, until wilted, about 1 minute. Remove the pan from the heat and stir in the vinegar. Return the onion-bean mixture back to the pan and season with salt. Serve warm or at room temperature.