250g butter, chopped
2 tsp finely chopped fresh tarragon
5 egg yolks
1 Tbsp white wine vinegar
Fine salt and finely ground white pepper, to season
This recipe makes 1.5 cups.
Put butter and tarragon in a small saucepan over a medium heat. Bring to the boil, then remove from heat and strain into a heatproof jug. Discard tarragon.
Put egg yolks and vinegar in the bowl of a food processor and process until smooth. With motor running, gradually add hot butter, in a slow and steady stream, until sauce thickens (if sauce splits, stir in 1 Tbsp ice-cold water). Season to taste. Serve over poached eggs.