Sauce Mousseline

Instructions

1. Prepare the double boiler
   Fill a saucepan with about 2-3cm of water and bring to a gentle simmer. Choose a heatproof bowl that can sit on top of the saucepan without touching the water. This will be your double boiler for making the hollandaise base.
2. Make the hollandaise base
   In your heatproof bowl, whisk together the egg yolks, cold water, and lemon juice until light and frothy. Place the bowl over the simmering water (ensuring the bottom doesn't touch the water) and continue whisking constantly. The mixture will gradually thicken. Be careful not to overheat or the eggs will scramble.
3. Incorporate the butter
   Once the egg mixture has thickened enough to leave a ribbon trail when the whisk is lifted, remove from heat. Very slowly drizzle in the warm clarified butter while whisking continuously. Start with just a few drops, then a thin stream, incorporating each addition before adding more. The sauce will become thick and glossy.
4. Season the hollandaise
   Add salt, white pepper, and cayenne (if using). Taste and adjust seasonings as needed. If the sauce is too thick, whisk in a few drops of warm water. Keep warm while preparing the cream component.
5. Whip the cream
   In a separate chilled bowl, whip the heavy cream until soft peaks form. Be careful not to overwhip - you want a light, fluffy texture that will fold easily into the hollandaise.
6. Combine and finish
   Gently fold the whipped cream into the warm (but not hot) hollandaise sauce using a rubber spatula. Fold just until combined, maintaining as much airiness as possible. If using tarragon, fold it in now for a fresh herbal note.