Adapted from Japan Centre
In a saucepan, melt the butter and cook the onion until translucent.
Turn the heat to low and add the flour, mixing well and cook 2-3 minutes until a roux has formed.
Gradually add the milk stirring constantly until the mixture thickens.
Add the crab sticks and season with salt and pepper.
Remove the mixture from the saucepan and cool completely.
When cooled, divide the mixture into 12 portions and make into croquette shapes.
Follow standard breading procedure with three separate bowls of flour, egg and panko crumbs. Dipping each of the croquettes into them until well coated.
Heat at least 2" of cooking oil in a medium pot and fry the croquettes until they are golden brown and crispy, about 2-3 minutes each side.