It's more a cool, refreshing taste-treat than a food. As the river is breaking up the new leaf buds swell and burst with tiny green leaves. These leaves taste good when they are very small and smooth, but about the time they get big enough to pick easily they also get tough and fuzzy-felty textured. All these different stages of willow can sometimes be available at the same time near a large snowbank. These bloom before breakup, while the snow is still on the ground and before any other leaf or flower.
Kids sometimes suck the sweet nectar.
Leaf-buds can be eaten when they are very young. Inupiat usually only eat sura - the young leaves. These are the mildest tasting sura and are best when picked off the stem individually. You may have to watch closely to catch them just right. If you don't watch, they will be too big - they grow fast in the warmth and continual light of springtime.