You can vary this a lot but the trick is to dice very fine whatever you choose to put in. If you can't find Pastina, you can use Stelline, or any of the very small star shaped pasta, but the Pastina seems to be the smallest of them all, and you want small here.
Stir in the Pastina and add enough water to make the total volume of liquid about twice the volume of the Pastina. Stir.
Cover. Reduce heat and cook until the Pastina is done and has absorbed all the liquid. Keep an eye on it because the Pastina can stick a little. Just stir it once if it appears to be sticking. If the water absorbs and it doesn't appear done then add just a tiny bit more. This only takes a couple of minutes.
Turn off the heat. Sprinkle the cheese over the top and cover. Do not stir.
The cheese will melt quickly. Now it's ready to eat. Enjoy.