Remove and discard any remaining section of root end and any tough upper green leaves. Slice leeks in half and run under cold water gently fanning the layers open to make sure all dirt and grit can run out.
Slice the cleaned leeks into quarters. Chop the quarters into chunks no wider than 1/3".
Add 5 cups chopped leeks to a large soup pot with olive oil and butter. Cook on high for a few minutes, stirring often with a spatula until leeks have softened and turned slightly translucent. If the leeks start to stick to the bottom of the pot, add 1/2 cup of the water and continue to cook.
Add the remaining water, the garlic, chicken bouillon, and black pepper. Bring to a hard boil, then turn down and simmer for 10 minutes.
Notes
Note: Additional garlic can be added if you are trying to fight off a cold or flu bug.