Heat some milk (water, cream, and chicken stock also work) in a pan until it’s just about to start simmering. 2-3 tablespoons per portion should be enough. Use a shallow pan with a wide base.
While the milk is heating, warm the pasta in the microwave for 5 seconds so it can be easily separated. Don’t worry if the sauce splits at this point.
As soon as the milk is ready, add the pasta to the pan and stir vigorously until the sauce re-emulsifies.
Once the sauce has re-emulsified, take the pasta off the heat and serve.
If the pasta is a little runny, turn the heat down and allow the sauce to reduce slightly. But remember that the sauce will firm up as it cools too.
The key with this method is the pan size. You want one with a large surface area so all of the pasta connects with the pan at the same time. The more points of contact, the faster the pasta will heat up and the less time it needs to spend on the heat.