3: Pour 5 tablespoons olive oil into a large non-stick pan on high heat. When good and hot add the chopped onion. Salt lightly and pepper. Cook for 1 or 2 minutes without colouring.
4: Add the leeks, mix well, but do not add any more salt. Cook, preferably uncovered or only half-covered (to keep the colour)...
5: ...until the leeks are barely tender. As the leeks are finely chopped this cooking is quite rapid.
6: Add 250 ml liquid cream, salt and pepper, then mix again and turn down the heat.
As stated above, we are aiming above all for a creamy, soft fondue, but with an attractive and appetising fresh green colour. This means we need to cook very finely sliced leeks as rapidly as possible, and not salt at the outset to avoid them giving off water.