Saving a split hollandaise
There is nothing more frustrating than a split hollandaise, turning it from a gorgeous thick emulsion to something that looks like it was brought up by the cat. This generally happens because the melted butter is added too quickly so that the eggs, which act to emulsify the fat and liquid, cannot keep up. When making a hollandaise you should whisk the butter into your sauce in a very slow drizzle, especially at the beginning. Once it thickens, you can start to add more quickly.
If your sauce does split, you can rescue it by starting a new batch and as that starts to come together slowly add the split hollandaise and whisk until it has been fully incorporated. This should save you having to throw the split sauce away.
Alternatively, you can use this foolproof blender method.