Put nuts or seeds into a high-powered blender or food processor. If your seeds and nuts have been soaked in salt water, then you will not need to add salt to the mixture. Otherwise...
Add ½ tsp salt.
Add sweetener if desired.
If needed, add a little mild oil to the nuts to assist in blending.
Process the nuts or seeds according the manufacturer's instructions.
If you are working with a food processor, simply put all of your ingredients into the bowl of your processor and start mixing. Keep it going for up to 12-15 minutes. You will need to stop occasionally to push the mixture down off the sides of the bowl, and you may need to add liquid oil, but you will supposedly end up with a butter at the end.