How to use onion tops?

Blanch them for no longer than 20 seconds and then make a pesto with parsley to balance the flavor. Toasted walnuts or cashews work well for nuts. I made a frittata for some clients using this onion top pesto, Gruyere cheese and Oregon morel mushrooms that was out of this world.

I like to saute them and use them as filling for filo pies, or tarts

I love using still tender onion tops just as I would use scallions. (I especially like them lightly fried in salted butter and scrambled with eggs.)

You can blanch and then puree them. Then add a bit of the puree to things like marinades (it would be really good in something similar to piri piri chicken/shrimp) or a pasta sauce.

pesto.

Use them in making stock.