Hollandaise

Steps

1. Clarify6 min
   low heat, undisturbed
   • butter
   butter melted and left to settle into three layers, then the clear gold middle poured off and the milky bottom discarded — that milky layer is water and casein, and both work against the emulsion. Let the clarified butter cool to warm; poured in hot it cooks the yolks on contact
2. Whisk2 min
   bowl off the heat
   • lemon
   • white wine vinegar
   yolks + lemon juice + cold water + salt (+ vinegar), until pale and slightly frothy. The acid does two jobs: it flavours the sauce and it lowers the pH, which raises the temperature at which the yolk proteins set and buys real margin against scrambling
3. Temper4 min
   bowl over barely-steaming water, base not touching it
   the yolk mixture, whisking constantly, until it thickens to the texture of pouring cream and holds a brief trail. Lift the bowl off every twenty seconds or so — the target is around 65°C and the yolk sets at about 70°C, and the gap between the two is smaller than a distraction
4. Emulsify6 min
   off the heat, a few drops at a time to start
   + warm clarified butter, whisking without pause, speeding to a thin stream once the sauce is visibly thick. Lecithin from the yolks coats each droplet of fat and keeps it separate; the whisking is what makes the droplets small enough for that to hold. Too much butter at once leaves droplets uncoated, they merge, and the sauce breaks into oil and curd
5. Season2 min
   warm, never hot
   to taste, loosening with a teaspoon of warm water if it is thicker than double cream. If it has broken, whisk a fresh yolk with a tablespoon of water in a clean bowl and dribble the split sauce into that — you are rebuilding the emulsion around new emulsifier, and it works. If the yolks have actually scrambled into grains, nothing recovers it; start again cooler