To make the cake batter, put the eggs and sugar in the upper part of a double boiler. Beat with a wheel egg beater for 10 minutes over boiling water. Remove from the heat. Stir in the melted butter; add the vanilla; mix and then gradually add the flour. Mix well. Spread in thin layers in 2 buttered baking tins.
Bake in a moderately hot oven (400°F.) about 15 minutes or until done. Remove from the oven and let cool. Using a thin, sharp knife trim off crusts and cut the cake in small squares.
Combine the ingredients for the filling. Spread it on half of the cakes; Cover these with the rest of the cakes. Leave plain or ice them with plain sugar icing; or sprinkle with confectioners' sugar. They are usually served in frilled cooky papers or petits four cups.