The food material is cooked, chopped fine, and held together with a thick white sauce. It is then shaped into small forms, as cone, ball, cylinder, etc., egged and crumbed and fried in deep fat about 2 or 3 minutes. This is a good way to use leftovers.
To Egg and Crumb - Use fine bread or cracker crumbs, or cornmeal. Beat eggs slightly in a plate, add 2 tablespoons water or milk, and 1/2 teaspoon salt. Dip croquette in crumbs, then in egg, and again in crumbs. See that all surface is covered.
Proportions for Croquettes - To 2 cups of the solid material such as fish, meat, chicken, vegetables, cereal, add 1 cup thick white sauce made of 3 tablespoons fat, 3 tablespoons flour, and 1 cup milk, stock, or gravy, and seasonings. The mixture must be just stiff enough to hold its shape. Cool, shape, egg and crumb, and fry in deep fat.
Potato Croquettes - 1 cup cold riced potato, 1/2 cup milk, 1/2 cup flour, 1 egg beaten separately, seasonings.
Mix, adding stiff egg white last. These do not require egg and crumb, but may be dropped from a spoon into the hot fat.
I cooked up some potatoes and mashed them, then browned some ground beef. After draining the fat, I added some garlic powder, nutmeg, and basil. I added salt and pepper to the mashed potatoes. I added 1 cup of meat to 1 cup of potatoe and then added the white sauce. Then I just egged and crumbed and fried in canola oil! :)