Place evaporated milk over low heat in a medium size pan until warm.
Beat egg yolks until thick and light lemon color, add sugar gradually. Remove milk from heat and gradually add to yolks while beating. Return to pan and place over low heat, stirring, until foam in the surface dissapear. Remove from heat before it boils (mixture must not boil). Add butter and mix. Pour in a bowl, cool and transfer to freezer.
Beat heavy cream as for chantilly and fold into cream from freezer. Return to freezer for 8 hours.
Whip egg whites slightly, add yolks and continue beating. Add sugar and beat for 20 minutes approximately. Reduce speed and fold in arrowroot, flour, salt, baking powder, melted butter and vanilla. Mix well. Pour batter into a jelly roll pan, previously lined with greased and floured parchment paper. Bake in preheated oven 400 °F (200 °C) for 12 to 15 minutes.Remove from oven. Invert over a lightly floured cloth on a horizontal surface and peel off paper.
Line a bowl with plastic film or aluminum foil to unmold easily. Cut cake and line sides and bottom of bowl, pressing carefully. Fill center with ice cream and cover with a round of cake. Press. Return to freezer.
Melt chocolate and combine with milks and sugar. Dilute cocoa in hot water and force through a strainer. Place all ingredients in a large pan and bring to a boil, stirring constantly, until mixture thickens and the bottom of the pan can be seen. Add butter and mix. Fudge must be thick. Cool.
Two hours before serving, unmold ice cream on a round platter and cover completely with chocolate fudge.
Introduce slivered almonds on top so that it resembles a porcupine.