Preheat oven to 180°C. Grease a square baking pan and sprinkle the bottom with flour.
Beat egg whites until very stiff.
Blend the butter with the sugar until white in color. Carefully add the egg whites, nuts and the sifted flour. Pour mixture in the prepared baking pan. Bake about 30 minutes. Cool completely.
Prepare the glaze: In a saucepan bring to a boil 300 ml. water. Pour the egg yolks and the confectioners' sugar in a mixing bowl and beat with the hand electric mixer upon the boiling water about 5-6 minutes or until mixture is white in color. Spread the top of cake with egg yolk mixture and refrigerate about 4 hours or overnight. Cut into squares and serve.
This cake is very good with pistachios too.