Pour the reduction into a saucepan and season it with the salt. Bring this to a boil. When the liquid is boiling turn down the heat and while blending with a hand blender add the egg yolk. This will add a lot of air to the mixture, and you don’t need to beat it as long as normal. Then use a whisk to beat it for another couple of minutes on a medium heat till firm peaks are forming.
Then directly turn off the heat and add the cold lobster butter. Gently mix it till the lobster butter is incorporated. Now a small trick. By adding a tablespoon of store bought mayonnaise you can stabilize the hollandaise and reheat it without splitting it. The stabilizers in the mayo will prevent it from splitting.
Now pour it into a syphon and charge it with two charges. The syphon will make the hollandaise a lot firmer and with will hold it’s form a lot longer as well.
You can keep the hollandaise in your fridge for 3 days and once needed just place the syphon under a heat lamp or in a warm water bath to easily heat it up.
