In a large pot add the olive oil, sliced white onion, garlic and onion powder and cook stirring for about 5 minutes.
Stir in the greens in batches.
Add 6 cups chicken stock and bring to a boil.
Add 1-2 yellow peppers. These peppers are hot so depending on your heat tolerance level I suggest 1-2. You may add more if you want it hotter.
Reduce the heat and simmer until the greens are tender, about 1 1/2 hours.
Add vinegar and salt and pepper to taste.