Scary Sprouting Garlic

Here's what happened to my head of garlic. I bought it three weeks ago and never used it. It sat in the corner of my kitchen counter, unnoticed and almost forgotten, until this morning. It's a bit scary, but really pretty at the same time.



So...

What can I do with it, besides watch it grow? Is it still OK to use? The green stalks are pretty pungent. Should I plant it? Help!