¼cupleftover vegetables OR leftover mashed potatoes OR more leftover meat
1tablespoonKetjap Manis (sweet Indonesian soy sauce) OR 2 teaspoons brown sugar + 1 teaspoon soy sauce
salt and pepper, to taste
For the breading:
¼cupmilk or cool water
enough vegetable oil, palm shortening, lard, or your favorite frying fat to fill a stock pot 2-3" deep
Prepare the gravy. Place the leftover gravy in a large bowl. If you're making a quick gravy, pour it in the bowl when it's finished cooking. (See the Notes for a quick gravy recipe.)
Grind the leftovers. Place the leftover meat, stuffing, and vegetables in the bowl of a food processor along with the onion, Ketjap Manis, and seasonings. Pulse to dice everything well, then process until smooth.
Create the filling paste. Dump the meat mixture into the large bowl with the gravy and stir together to create a cohesive paste. The paste should hold together easily but not be super sticky. If it's too dry, add more gravy. If it's too sticky, you may add a small amount of flour OR grind more meat or stuffing to mix in.
Form the croquettes. Cover a baking sheet with parchment paper, then shape the paste into little logs and lay them on the baking sheet. Aim for logs that are about 3" long and 1" in diameter - they'll look like fat little breakfast sausages. Alternatively, you can roll them into balls about 1 ½-inch diameter, which are called bitterballen rather than kroketten.
Prepare your breading station. Create a breading station using three bread pans or other rectangular containers. In the first pan, add the flour. In the second pan, lightly whisk the eggs and milk together. In the third pan, mix together the breadcrumbs, salt, and pepper.
Bread the croquettes. Roll each croquette log in the flour, then submerge it in the egg-milk mixture, then roll in the breadcrumbs, tapping off the excess after each step. Return each breaded croquette to the baking pan. You'll be cooking them in batches of 5-8 croquettes at a time, depending on the size of your pan.
Preheat the oven and heat the oil. Pour the oil into a heavy-bottomed pot with tall sides, such as a stock pot, until the oil comes up the sides by 2-3 inches. Clip a candy thermometer to the side if you have one. Turn the heat to medium-high. Preheat oven to 200°F and place a baking sheet lined with parchment paper on the middle rack.
Cook the croquettes. When the oil has reached 360°-370°F, add the first batch of croquettes. (See how to test the oil temperature if you don't have a candy thermometer in the Notes section below.) We cook in batches so that the oil temperature doesn't plummet too much when the croquettes are added, which would result in greasy, soggy croquettes. Cook until the outsides are deep golden-brown, about 6-9 minutes, turning them over about halfway through cooking. Place finished croquettes in the oven to stay warm. After each batch, return the oil to 360°-370°F again before adding the next batch.
Serve the croquettes. The croquettes can be eaten plain or dipped in mustard. The only question is whether you want classic yellow mustard, Dijon-style, or seedy brown. The choice is up to you!
Don't have leftover gravy? No problem!
Make this quick gravy:
4 tablespoons butter
6 tablespoons all-purpose flour
1 1/2 cups milk or chicken stock
In a heavy-bottomed saucepan, melt the butter over medium heat. Add the flour and whisk until smooth. Let the mixture bubble for 1-2 minutes until the top appears dry, whisking occasionally. Pour in the stock in a few tablespoons at a time, whisking after each addition.
If you're making this at times other than Thanksgiving, other meats work well too, such as shrimp, cooked sausage, or beef pot roast. Adjust your seasonings accordingly (for example, Thanksgiving stuffing may not be the flavor you're looking for if you use shrimp.)Basically, this is the ratio you're looking for: 1 1/2 cups gravy/roux to 2 1/2 cups meat filling (as measured before it's ground to paste) plus seasonings. If you stick to that ratio, pretty much ANY leftover can be used inside these tasty treats.
How to test the oil temperature if you don't have a thermometer
When you're cutting the onion, cut one thin slice across the grain (the direction so that when the onion is cut the rings are shaped like a rainbow). Break the rings apart into strings and set aside. When it's time to test the oil temperature, dip one onion string into the hot oil. At 360°-370°F, the oil should vigorously bubble when the onion is dipped with a lovely sizzling sound, but it shouldn't violently roil or pop or sputter (too hot), nor should it just send up little bubbles like a fizzy soda (too cold). It also shouldn't be smoking, but that may vary slightly depending on what type of fat or oil you're using. You'll want to test the temperature again with a fresh onion string between each batch of croquettes.
A quick variation:
Since all the ingredients in croquettes are already cooked, the filling itself is safe to eat before frying. Some of our family members actually prefer the filling used as a spread on crackers rather than the finished croquettes, so experiment to see what you like best!
Thanksgiving Leftovers Kroketten (Dutch Croquettes) from https://nourishingjoy.com/thanksgiving-leftovers-kroketten-dutch-croquettes/