The tender stems on Swiss chard are an edible, crisp and juicy bonus to the leaves and just need a few minutes of cooking to soften in this easy weeknight dinner. Leaving some of the starch on the canned beans adds silky texture to the juices that come from the chicken sausage and gently thickens them as well.
Preheat the oven to 425˚ F. Line a baking sheet with foil. Toss the sausages with 1 teaspoon olive oil on the pan and bake, turning occasionally, until browned and heated through, about 15 minutes.
Meanwhile, slice the chard stems and roughly chop the leaves. Heat the remaining 2 tablespoons olive oil in a large nonstick skillet over medium-high heat. Add the chard stems and leek and season with salt and pepper. Cook, stirring occasionally, until tender, about 5 minutes.
Add the beans and garlic to the skillet and cook, stirring, until softened, about 1 minute. Gradually add the chard leaves, stirring to wilt. Add the heavy cream and chicken broth and simmer until the vegetables are soft and the beans are creamy but not soupy, about 3 minutes, adding a few splashes of water if the pan seems dry. Remove from the heat and stir in the vinegar; season with salt and pepper.
Divide the beans and greens among shallow bowls. Slice the sausages and add to the bowls; sprinkle with the parsley.