Rinse the turnip greens thoroughly in cold water
Remove any tough stems or damaged leaves
Chop the greens into bite-size pieces
Heat oil or butter in a large pot over medium heat
Add chopped onion and garlic if desired
Cook until softened
Add the turnip greens to the pot
Stir until the greens begin to wilt
Add water, broth, or stock to cover the bottom of the pot
Season with salt, pepper, and optional red pepper flakes
Cover and simmer over low heat until tender
Stir occasionally and add more liquid if needed
Taste and adjust seasoning
Serve hot