2 egg yolks
2 tbsp. fresh lemon juice
1/2 c. very cold butter

Stir the egg yolks and lemon juice with a wooden spoon in a small heavy saucepan. Keep the heat low and stir briskly all the time. Add half the butter and stir until it has melted. Then add remaining butter, stir again until it has melted and the sauce has thickened. Serve at once. Good as a dip for steamed artichokes.