Hollandaise is known as one of the mother sauces in classic French cooking. Along with mastering a roux sauce or mayonnaise, hollandaise is one of those that you really need to master for your cooking repertoire. It also forms the basis of sauces such as Bearnaise which is a perfect foil for steak and of course you cannot have eggs Benedict without this rich and creamy sauce.

The key to this recipe is the gastrique, which is a reduction of white wine vinegar or white wine (I sometimes use white vermouth), with mace, bay leaf, peppercorns and shallots. This gives the sauce its base acidity and depth of flavour, I consider it the most important part. The one mistake that is often made is that raw vinegar or lemon juice is used for the acidic base, this results in a harsh and unpalatable sauce. By reducing the vinegar you have taken away the harshness but retain a light acidity and good flavour from the shallots and herbs.

When I first learnt this sauce at Leiths, we made it using clarified butter, which is heating the butter before boiling point and then straining it through a fine cloth to remove the milk solids. It's up to you if you wish to go this far with the recipe.

Gastrique
100ml white wine vinegar
1 bay leaf
1 blade of mace
4 peppercorns
1 shallot roughly chopped

Place all ingredients in a pan and bring to the boil, reduce until it has reached 25% of it's volume
Strain and place in an airtight container
This will keep in the fridge for several months

Hollandaise
2 egg yolks room temp
200g unsalted butter
5-10ml gastrique 
2ml lemon juice
salt and pepper

By hand
Melt the butter and allow to cool slightly
Place the egg yolks and 5ml of the gastrique in a bowl
Place the bowl over a pan of lightly simmering water (don't let it get too hot otherwise it will cook the eggs and split the sauce)
Start whisking the egg yolks and slowly add the warm butter continually whisking until it starts to thicken
Once thickened, take off the heat and season with the lemon juice salt and pepper to your taste
If you prefer more depth you can add a little more gastrique

With a food processor
Place the egg yolks, and gastrique into the smallest bowl your food processor has, start the machine and add the warmed butter very slowly until it starts to thicken
Season with salt and pepper and the lemon juice

With a hand blender
Place the egg yolks and gastrique into a tall jug
Start the blender on it's highest setting and add the butter very slowly until it starts to thicken
Season with salt and pepper and the lemon juice

Sous vide and whipping siphon method (based on modernist cuisine method)
For this recipe you only need about 120g melted butter, 3 egg yolks and 10ml of gastrique
Vacuum pack the egg yolks, gastrique, melted butter, salt, pepper and lemon juice or place in a ziplock bag
Place in the sous vide at 65c for 30 minutes
Ensure you keep moving the mixture around the bag every 10 minutes or so to ensure the eggs do not solidify
Once the mixture has cooked you can whizz in a blender to ensure it is smooth
Pour this into a whipping siphon, ensuring you sieve the mixture while doing so
Charge the siphon with gas and shake well to incorporate
The hollandaise can now be kept to one side in the water bath at 55c until such time as you wish to use it

Bearnaise
This is made with the addition of glace de viande and tarragon. Glace de viande is a highly concentrated version of brown stock. The stock is reduced slowly until it forms a nice glazed/sticky reduction. 

When making bearnaise I like to add a few sprigs of tarragon to the gastrique to add some extra flavour
The only variation to the aforementioned method is to add 5ml of glace de viande with the egg yolks and gastrique when making the base hollandaise.
To finish add 10g chopped fresh tarragon to the sauce and season
If using dried tarragon use 5g