Pecorino's proteins tighten up and squeeze out fat when they get too hot. That's how a sauce turns into a rubbery lump in a pool of water.
The fix for next time
- Grate the cheese very fine, on the smallest holes you have.
- Mix it into a paste with a little slightly cooled pasta water, in a bowl.
- Add the paste off the heat, once the pan has stopped sizzling.
Can I save it?
Sometimes. Move everything to a cool bowl, add a spoonful of warm water and stir hard. If it's fully seized, it won't come back smooth. It'll still taste good, so eat it with extra pepper and try again next time.
Other things that help
- Cook the pasta in less water, so that it's starchier.
- Avoid pre-grated cheese, which often doesn't melt as smoothly.
