I've been experimenting with making green thai curry paste this week and I have a pretty decent tasting curry resulting right now. However, in all the green curry paste recipes I see, they say I have to add onion/shallots to my paste when crushing in the mortar.
My question: Is it necessary to have onion/shallots present in the paste? Or can I make a green curry paste without onion, then just add onion to the actual curry when I use the paste to make a full on dish from it? Is there any cooking theory behind this as to why onions must be crushed in the paste as opposed to just added later when cooking the dish? Will it affect the taste of my curry in any noticeable way?
The question is more from a practical perspective, as I have a pretty small mortar, and adding the onions/shallots tends to cause it to overflow and make crushing pretty difficult.