How to cook young onions so that they melt? I was at a restaurant yesterday and I was surprised to get young onions (sorry for the direct translation from French oignon nouveau en botte - I added a picture below) cooked as whole, but melting once they are cut.



What I got on the plate was just the head (without the green part), cooked but not fried/braised (the head was white). When cutting it, the layers fell apart and the taste was almost sweet, without any aggressive onion taste. If I did not look closely at what I was eating I could miss the fact that it was an onion.

What would be the right approach to cook an onion like this? Boil it and then sauté? Cook it in butter for a long time at a low temperature?
Oignons nouveaux, aka green onions, are typically cooked low and slow in a dutch oven with butter or [olive] oil. When you're cooking them (and onions in general), salt them early - salting the onions will help get rid of that "oniony" taste and will let you taste their natural sweetness.