4 egg yolks
2 teaspoons fresh lemon juice
1 tablespoon water
1 tablespoon Dijon mustard
2 teaspoons finely chopped parsley
1/2 pound butter, melted and warm
In a stainless steel bowl set over a pot of simmering water over
medium heat, whisk the egg yolks with the lemon juice, water,
mustard, and parsley, together. Season with salt and cayenne.
Whisk the mixture until pale yellow and slightly thick. Be careful
not to let the bowl touch the water. Remove the bowl from the pot
and whisking vigorously, add the butter, 1 teaspoon at a time,
until all is incorporated.