Saute the onion with margarine in a frying pan.
When the onion is translucent, add the flour and continue sauteing.
If you cook it thoroughly here until any flouriness is gone, it won't form lumps later.
Add soy milk little by little, in 4-5 batches. Mix well to form a paste.
Season the paste with salt and pepper. Add the canned crabmeat, liquid and all.
Mix for 2 to 3 minutes over heat. The sauce may be a bit loose here, but it will firm up when it's chilled so don't worry.
Put the sauce into a shallow container, and chill in the refrigerator for 3 hours.
Divide the sauce and form into croquettes. Coat each one with flour, egg and panko, and deep fry in 355°F/180°C oil until golden brown.
Story Behind this Recipe
I made crab cream croquettes using canned crabmeat. It's healthier because of the soy milk.
By using the whole can of crab meat, liquid and all, you get all the crab flavor in there. If you want the crab flavor to be more pronounced, saute the crab meat in a separate frying pan before adding to the cream sauce. I fried king oyster mushrooms along with the crab meat too.