If this is your first time making jam, you may be wondering how you know the jam is done. There's a whole thing online about the frozen plate method (basically, you put jam on a cold plate, touch it, and see if it wrinkles). But that just makes this easy recipe more complicated than it needs to be. So, you just have to watch it. You'll see it changing. It starts as three separate ingredients. Then, the sugar starts to melt down and the mixture becomes foamy and bubbly. The foam then dissipates and the mixture gets darker. And then, finally, the mixture gets really thick and resembles the texture of store-bought jam. That's when it's done. You want to make sure you remove it when it's done. You can leave it an extra minute just to make sure, but that's it. If you overcook your jam, it'll become really solid when it cools completely and it won't be spreadable at all.