This is an easy food to find at this time of year but one that is not highly regarded. It's more a survival food than a nourishing meal but in times of desperation it might be handy to know. Finding the willow is easy enough but wait till the catkins have pollen on the anthers before eating..
There are over 300 species of willow world wide and I certainly don't know them all though I'm pretty sure this is goat willow, it's quite common all around me here. It produces little furry catkins often called pussy willow which then blossom into the edible catkins we see here.
I have read that native American tribes have eaten the full catkins in a cooked mash, but I've never tried this so it's one for the future, but you can eat the stamens seen here, just nibble them off with your teeth. They have a bitter taste but are relatively palatable.
Important thing to remember is that the salicin that may be in the catkins reacts in your stomach to form salicylic acid and this may prove a problem for some people, even causing stomach upsets, so be wary especially if you are already on some sort of medication that could react with natural aspirin.