I'd like to make a soup that uses cashews for much of its flavor. For some reason, I can only use a limited number of cashews, but I can use them in any way I want.
How can I get the most cashew flavor into the soup?
By maximising first the flavour of every single nut and then maximising the surface:
Gently roast the cashews, then grind them finely.
If the resulting "gritty" texture is not to your taste, grind them further until you get a nut butter, which should dissolve nicely especially in cream-type soups.