Stir your leftover mashed potatoes to loosen them up.
To the leftover mashed potatoes add the flour, 1 tsp of the chopped chives, garlic, eggs, salt, and pepper. Taste and see if you need more salt and pepper, depends on how seasoned your original mashed potatoes were.
Stir together until smooth making sure there are no lumps of flour.
In a frying pan, add a few tablespoons of oil, just enough to coat the bottom of the pan really well. Put the heat to medium and let it heat up. Once you see the oil shimmering, I like to put the end of a wooden spoon in the oil and if it forms a lot of bubbles around the handle, your oil is hot and ready.
Using a large spoon scoop some of the potato cake mixture and gently place it into the oil, gently pressing down a little to form a cake. It will be about 1/2 inch thick.
Let it cook about 2 minutes on the first side. Once you notice the edges browning nicely you can take a peek and see how the bottom is looking. Once browed, flip your potato cake. Cut the second side for about 2 minutes also.
Once both sides are nicely browned, remove and place onto a paper towel-lined plate and sprinkle with some salt.
Repeat for the remaining potato cake mixture, adding more oil if needed to the pan.
Sprinkle with the remaining chives and serve alone or with some sour cream.