Egg-based sauces, like hollandaise, are ones that everyone should know how to make. Next time you have one you want to add to a hot dish (like pasta), take the pan off the heat or else you'll end up with a clumpy, scrambled mess.
As Chef Michael White demonstrates in the video above (fast forward to 3:40), completely move your pan off the stove and onto a cool surface before pouring your egg-based sauce in. Mix the dish together so the sauce smoothly coats everything, then serve. You don't want to leave the sauce in the pan too long (even after removing from the heat) because the warmth of the pan can cook the sauce. Just this small extra step will leave you with a much better dish.
Make Pasta From Scratch with Two Ingredients [Bon Appetit]