DAE add a splash of the pasta water to the sauce right at the end
So I was at this little spot in Providence back in March, watching the line cook finish a plate of cacio e pepe. He pulled a ladle of the starchy pasta water and whipped it into the pan of cheese off the heat, and the whole thing went silky in like 10 seconds instead of clumping up like mine always does. Been doing it at home for 3 months now and I haven't had a single broken sauce since. Turns out the starch is what holds the fat and cheese together. Anyone else got a trick like this that a line cook showed you once and you never stopped using?