1. Remove the root and tough outer leaves of the leeks.
Slice them into desired size rounds, then wash them thoroughly (there is often dirt trapped between the leek leaves...)
2. Heat the olive oil in a large sauté pan, then add the leeks.
Let them sauté for 1-2 minutes while stirring, then cover.
3. Cook for about 20 minutes over medium heat, checking occasionally to ensure there is a bit of leek water and that it doesn't burn.
4. After this time, extract the juice from the orange and half of the zest, then add to the leeks.
Also add the cumin, salt, pepper to taste, then mix well.
Let it finish cooking for about 10 minutes covered.
Uncover at the end if the fondue is too liquid.
5. No waste: Feel free to add the "tender" green part of the leeks to the fondue, as it will flavor it more than just the white part of the leek alone.