The dark green part of the leek is often discarded because it is usually quite tough.
You can however give it a second life in the kitchen, not only does it not go to waste, but you get something tasteful too.
A super easy way to use the green leaves is to put them in vegetable stock with the other vegetables.
Another way is to cut them up and add them to a vegetable soup.
Boil the green part until tender and then add it to beaten eggs to make an omelette.
Also, if you cut the dark green part of the leek into very thin strips, you can flour them lightly and then dip them in hot oil to make crispy chips.