Hardware needed:
- a stick blender
- a tall container with an inner diameter not much bigger than the stick blender head
- (recommended) a tool to press out the lemon juice
- (recommended if you're unexperienced with seperating eggs using their shells) a tool to seperate eggs
- a way to melt the butter (but not heat it up too much)
You will need:
- 250g butter
- 3 - 4 fresh eggs. Important: They must be less than a week old, the fresher the better
- a lemon
- a teaspoon of mustard
- salt & pepper
Melt butter
You start by melting the butter. I use a small covered pot on lowest heat. You want it to be liquid without any solid blocks. I start the process when the butter has turned opaque without any solid pieces visible. It's important to keep the butter below ~56 °C because we're not cooking the egg.
Prepare eggs and lemon juice
While melting the butter you can work on juicing the lemon and seperating the eggs. We only need the egg yolks (I keep the leftover egg white for later and add it to my solution when I make scrambled eggs for example).
Note: It's important that you separate the egg yolk nicely so that no egg white gets into the mixture as it will hinder the emulsification.
The magic
Add egg yolk and lemon juice to the tall container. When the butter is liquid, put the stick blender into it, start and slowly add all the butter to it. It will emulsify nicely.
Then to taste add salt and pepper. I also like to add a bit of mustard and some sichuan pepper.
Storage: Keep in the fridge, use up quickly.