• 1/2 cup butter 
• 1 cup sifted confectioners sugar 
• few grains salt 
• 1 teaspoon vanilla 
• 1 egg or 2 egg yolks, well beaten. 

Cream butter; gradually add sugar and beat until well blended. 
Beat in salt, vanilla and eggs; set over hot water. 
Cook and beat with wire whisk until it has thickened and is smooth and light - about 7 minutes. 
Serve hot or cold. 

Yield: 1 1/2 cups