Cold rice straight from the refrigerator can do things fresh rice cannot: its grains have firmed up and dried, so they do not stick together when fried in a pan or turn mushy when mixed into a filling. Pan-fried rice, rice patties, fritters, and stuffed-vegetable filling all turn out better with leftover rice. These methods are for rice that was cooled and refrigerated soon after cooking.
As rice cooks, the grains absorb water and the starch swells and softens, which is why hot rice is moist and sticky. As rice cools, the starch reorganizes, the grains firm up, and their surfaces dry. This is what makes cold rice look hard and dry, but the same change prepares it for a second cooking. Dry, firm grains hold onto oil in the pan and brown; moist grains steam, clump together, and stick to the bottom of the pan. The dryness that seems like a flaw in leftover rice is exactly what is useful here.
The most direct use is pan-fried rice. Heat a wide pan thoroughly, add a little oil, and first sauté firm vegetables such as carrots, peppers, and onions. Crumble the cold rice with your hands as you add it; if you try to break up clumps with a spoon in the pan, the grains will break. Spread the rice across the pan and leave it alone for a while. Turn it when the grains separate and start sliding around the pan. Near the end, scramble and cook an egg at one side of the pan, then mix it into the rice. Check the salt at the end because the rice was already cooked with salt.
The second use is as a filling. Knead cold rice with egg, grated cheese, chopped herbs, and a little flour; if the mixture holds its shape in your hand, shape it into patties or flat fritters and fry them in a pan. Fresh rice gets crushed and pasty in this mixture, leaving the center of a patty mushy; cold grains hold their shape and give the patty a grainy texture. If the mixture falls apart, add a little more flour; if it is firm, add a spoonful of yogurt. Adjust the amount by hand according to how dry the rice is. Turn a patty when its underside is browned; a rice patty turned too early will fall apart.
Leftover rice can also go into stuffed vegetables, with one difference. Filling made with uncooked rice cooks in the pot as it absorbs water; filling made with cooked rice has already absorbed its water. So reduce the water added to the pot, and stop cooking when the leaves or vegetables are tender; if you wait as long as you would for raw rice, the filling will turn mushy. A small amount of leftover rice can also go into soup: add it to meat or vegetable broth in the final minutes and keep it there until the soup returns to a boil and the rice is steaming hot throughout; rice simmered longer will cloud the soup.
The type of rice also determines where it works best. Plain rice cooked with butter works in any of these dishes. In rice with orzo, the orzo browns before the rice in the pan and can burn, so lower the heat a little. Pilafs with chickpeas, vegetables, or iç pilav (rice with liver and nuts) can go into patties with their own ingredients, so there is no need to add extra vegetables. Tomato rice catches in the pan more quickly because its tomato paste tends to burn; stir this rice often while frying it. Rice that has been left on the counter for more than 2 hours should not be used in any of these dishes; discard it.