When you cook rice, the starches absorb water and become gelatinous. But as the rice sits for a day, the starches start to break down and reorganize, making the rice drier and more separate. This process is called starch retrogradation, and it's the key to making perfect fried rice.
Now, you might be thinking, "But what about leftover rice from last night's dinner? Can't I just use that?" Well, technically, yes, you can use leftover rice, but it's not always the best option. This is because leftover rice can be too dry or too oily, which can affect the flavor and texture of your fried rice.
So, what's the best way to make day-old rice? Plan ahead, that's what! Cook a big batch of rice the night before, and then let it cool and refrigerate overnight. This will help to stop the cooking process and allow the starches to retrograde, making the rice perfect for fried rice the next day.