Huevos Haminados (Sephardic Jewish-Style Eggs) - cooking recipe

Ingredients

6 eggs
1/8 teaspoon pepper
1 teaspoon salt
1/2 teaspoon ground coffee (optional) or 1/2 teaspoon tea leaves (optional)
3 -4 yellow onion skins, the outer layers (the more, the better!)
1 -2 garlic clove, chopped (optional)
1 teaspoon vegetable oil
1 teaspoon vinegar

Preparation

Place all ingredients into a pot or crock pot, and cover well with lukewarm water.
Bring water to a boil, cover and reduce the heat to very low. Cook for at least 5 hours or (preferably) overnight. As water evaporates, more can be added.
After the eggs have been cooking for several hours, you can gently tap the shells with a spoon to crack them, and continue to cook. This will cause a beautiful marbled color to form on the egg whites.
Drain the eggs, rinse the shells and refrigerate until ready to use.