Put all ingredients in a large mixing bowl. (Try to sprinkle the salt evenly over the entire surface area of the mashed potatoes so you don't accidentally get a super salty bite.)
Get in with your hands (or a wooden spoon or spatula if you're not a handsy person) and mix everything thoroughly.
Divide batter into 4 equal parts and form each fourth into a roughly 4.5 inch diameter patty.
Heat the 1/4 cup oil in a fry pan to medium high.
While the oil is heating, coat the patties on all sides with a little bit of flour.
Fry the croquettes, two at a time, for 4 to 5 minutes per side. You'll know the oil's ready if you hear a gentle sizzle when you throw a pinch of flour into the pan. If you don't see that flour cooking and hear it sizzling right away, your oil's not hot enough yet and you should wait, otherwise your croquettes won't sear immediately, and they'll absorb too much oil and be greasy. If the croquettes are browning too much before the 3.5 minute mark, turn the heat down a touch.
Enjoy!
