How to cook young onions so that they melt?

Question

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?

Answer 1

I usually steam them until they are soft in bulk and then store them in fridge. When I need to use them I just throw on butter. I don't use much salt when steaming but I always taste the green part. If it have this spicy (but not oniony) taste I brisk the heads in cold water for a second and then put them on steam (I don't keep them in the steamer from the beginning).

Usually keeping vegetables cold or even freeze them for a short while will bring the sweet taste.

Answer 2

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.