Stir eggs and sugar into top of double boiler until creamy and lukewarm. Remove from heat and beat until cool; add flour gradually, mixing well. Fold in butter and vanilla.
Use special shell-shaped Madeline molds that have been buttered and floured (or small 1 1/2 inch muffin pans). Fill molds 2/3 full; fill muffin tins less than 1/2 full. Bake in a 425 degree oven for ten minutes or until lightly browned. Dust cooled tea cakes with powdered sugar. Yield: 5 dozen.