A smooth and creamy classic sauce.

6 tbsp dry white wine
3 tbsp white wine vinegar
two shallots, finely chopped
four-six crushed peppercorns
225g (8 oz) unsalted butter, in cubes
three large egg yolks
1 lemon, juiced
salt and freshly milled white pepper

Put the wine, vinegar, shallots and peppercorns in a small pan, and boil until the liquid has reduced to 2 tbsp.
 
Melt and heat the butter in a small pan until boiling.

Press the wine mixture through a fine-mesh sieve into the blender jug.

Add the yolks quickly to the reduction, then add the lemon juice and season.

With the blender spinning on Speed 1, pour in the very hot butter, leaving behind its milky residue, in a steady, gradual
stream through the hole in the lid until all is emulsified, and the sauce is thick, smooth and creamy.

Check the seasoning again: add more lemon juice, salt and pepper to taste.
 
Keep the sauce in a warmed thermos flask for a short time, or serve immediately.