Heat a large, deep skillet over medium-high heat. Add the oil to the skillet and swirl it around. Add the onion, salt, and pepper and cook for 5 minutes, or until onion is slightly golden. Cover the skillet, reduce the heat to low, and cook the onion for another 5 minutes, or until soft and beginning to brown. Stir in the garlic and cook, uncovered, until fragrant, about 3-4 minutes. Add the thyme and cook for 2 minutes.
Add the beans to the skillet, along with the vegetable stock/water. Raise the heat, bringing the mixture to a boil. Reduce the heat to low, cover the pan, and simmer for 5 minutes. Remove the lid and cook for another 5 minutes, or until the mixture is creamy and the beans are very soft. You can crush some of the beans with the back of your spoon or a potato masher if you’re looking for an even creamier texture. Add the liquid smoke, if using.
Add the greens to the skillet and continue to cook until they have wilted slightly.
Stir in the apple cider vinegar and more salt and pepper, to taste. Serve immediately with crusty bread. Fully cooled and covered leftovers will keep in the fridge for up to 4 days.