Can I freeze chopped onions and/or chopped leeks?
I don't see why not...I've actually seen frozen chopped onions at the grocery and one year when we had an overabundance of leek in the garden, I froze the white and light green part to use in soups and stews. I also think freezing does take away some of the "bite" though.
Hey bstar! Definitely freeze them and make stock with them!
Generally I blanch them for 30 seconds, dunk them in an ice bath, drain and then freeze.