You could be professionally trained in cooking and still manage to separate your hollandaise. It’s a fact of the kitchen, emulsion sauces sometimes “break” or separate. However, there are tricks you can use to fix your sauce.
The main reason your sauce will separate is because your hollandaise is too thick. Below are two solutions for fixing this problem:
Gradually whisk in 1/4 part hot water to your broken hollandaise. Add 1 tbsp hot water at a time until your hollandaise begins to come together. Continue to add the water gradually until your sauce is the right consistency.
Note: You can use scalded cream instead of hot water.
In a fresh bowl, start with an egg yolk or 1/2 cup pasteurized egg product. Slowly whisk or blend in your separate sauce into the egg.
If either of these methods isn’t able to salvage your hollandaise, you’ll have to restart. Likely something other than the thickness of your sauce is the cause of its separation. When you do start a fresh sauce here are some pointers to prevent you sauce from breaking:
Pour your butter in slowly. Too fast and it won’t properly incorporate.
Add 1 tsp Dijon mustard to your bowl or blender before you add in the eggs. The mustard with stabilize your sauce and will prevent it from separating.
If you notice your hollandaise is too thick while whisking or blending, add 1 tbsp of hot water before you sauce has a chance to separate.