Any hardy, leafy green vegetable works well in this recipe, and it’s a great way to use up extra beet or radish greens. If you’re using kale, chard, beet, or collards, separate the tough stems from the tender leaves and saute them with the garlic to ensure they soften a bit before serving.
Warm the olive oil in a wide skillet over medium heat, and then stir in the garlic and crushed red pepper. Cook the garlic until fragrant, about 2 minutes, and then toss in the greens until well-coated with olive oil.
Pour in the chicken broth, and let the greens simmer until crisp-tender and most of the liquid has evaporated, about 5 minutes. Sprinkle with vinegar and adjust seasoning with salt, then serve.