Preheat the oven to 375°F. Whip the 5 egg whites with 1tablespoon ice water and apinch of salt until stiff.
Add the egg yolks, one by one, beating for 1 minute after each addition.
Add ½cup of the sugar, spoon by spoon, whipping all the time. (If you are using an electric mixer, turn down to lowest speed.) Add flour, little by little, making sure that it is completely blended into the egg mixture.
Line a baking sheet 17 by 12inches with wax paper, and lightly spread it with 2tablespoons butter. Pour the batter on the baking sheet. Tap sides a few times to even it out.
Bake in the preheated oven for 10 to 12 minutes, until golden brown.
Cut the cake into 6 even pieces each 8½ by 4inches. Pull off the wax paper. Cover the pieces with cloth or fresh wax paper while cooling inorder to retain some of the moisture.
Make the chocolate filling.
Set aside the best of the 6pieces of pastry to use for the top of the cake. Spread alittle sweet butter on a marble slab or Formica-topped table, and place the chosen cake layer on it.
Spread the chocolate filling on the other 5 layers; the filling layers should be about ⅛inch thick. Put the layers together and frost the sides. Put the rest of the filling in a pastry bag.
Melt the ⅛cup sugar in a heavy frying pan; stir it with a buttered spoon as it cooks over very low heat. The sugar at first will look like dirty snow, then it will dissolve into a walnut-colored shiny liquid. Immediately remove it from the heat and spoon it directly from frying pan onto the top cake layer on the marble slab. Score it to intended portion sizes with the tip of a buttered knife, then cut it all the way through with the buttered knife. You must work fast because the caramel hardens in less than a minute. Be careful not to touch sugar with your hands.
When the caramel is cool, put the top layer on top of the filled layers. The shiny glaze is the crowning glory of the cake. Fit a No. 6 tube to the pastry bag and pipe a decorative border of chocolate filling around the top edge of the torte.
Cool the cake in the refrigerator until the filling is firm, 3 to 4 hours.
Slice the cake with a knife dipped into hot water. Cake will keep in refrigerator for as long as 10 days.