Really easy version of this amazingly versatile sauce, try it with some poached eggs on toasted sourdough
Put your white wine vinegar, peppercorns and shallot into a small saucepan with little drop of cold water. Heat gently until at a simmer, then reduce until only 2 tbsp of liquid remain. Strain and cool.
Chuck your butter into a little saucepan and melt until just beginning to bubble
Now the complicated bit, you're going to cook your hollandaise over a bain marie, which is basically a heatproof bowl set over a pan half-filled with gently simmering water, don’t let the bowl touch the water though as your egg yolks will scramble, put the reduction into your heatproof bowl and add the egg yolks and whisk for 1-2 minutes until the eggs and the reduction have combined, now slowly pour in your melted butter, whisking all the time until the sauce starts to emulsify, keep going until all your butter is in, your sauce should now thickly coat the back of a spoon.
Taste and season with salt and for acidity add your lemon juice, cover with cling film and set aside until needed