Forgot to take your half-and-half out of the fridge when you started cooking? Put it in the microwave for 15-20 seconds. You want it to be lukewarm/room temperature so it doesn’t shock up when you put it in the skillet.
Reheating? I don’t recommend it, but if you need to, I recommend reserving a bit of the pasta water and reheating it with 2-4 tablespoons of the pasta water on the stove over low-medium heat until heated through and the sauce has loosened.
Possible add-ins: chicken, shrimp, or broccoli. See the blog post for more ideas!