This recipe goes along with the Lobster-Stuffed Beef Tenderloin post but I thought it might be helpful to separate them, in the event you might just be looking for a béarnaise sauce!
Making béarnaise sauce isn't too difficult, you can of course buy one of those packages at the store and make it that way too. :)
Recipe courtesy of Emeril Lagasse
2 tablespoons chopped shallots
4 sprigs fresh tarragon
1/4 cup dry white wine
1/4 cup dry vermouth
4 large egg yolks
1 cup (2 sticks) melted unsalted butter or clarified butter
1 teaspoon fresh lemon juice
2 tablespoons chopped fresh tarragon leaves
1/2 teaspoon salt
1/8 teaspoon ground white pepper
In a small saucepan, combine the shallots, tarragon, white wine, and vermouth. Bring to a boil and cook until reduced to 2 tablespoons.
Remove from the heat, strain, and cool.
In the top of a double boiler, or in a metal bowl fitted over a pot of barely simmering water, whisk the egg yolks and reduced wine until ribbons start to form. Whisking constantly, drizzle in the melted butter a bit at a time until all the butter is added and the mixture is thick. Remove from the heat. Whisk in the lemon juice, chopped tarragon, salt, and pepper. Adjust the seasoning, to taste.
Cover to keep warm until ready to serve. To serve, place in a decorative bowl with a small sauce ladle.