Preheat the oven to 350°F; butter and flour a 13 x 9 baking pan.
In a bowl combine the walnuts, cinnamon, cloves, allspice, breadcrumbs, flour, and baking powder.
In a small glass, dilute the soda with the cognac.
Beat the egg whites in a bowl until stiff peaks form.
In a large bowl mixing bowl, cream the butter with the sugar and then add the eggs yolks; mix in the soda with the cognac, and add the milk and the walnut mixture, beating until well combined; fold in 1/4 of the beaten egg whites to lighten batter, then carefully fold in the rest; it is ok if a few white streaks show in the batter; spread into the prepared baking pan.
Bake for 45-60 minutes, or until the cake tests done. Cool cake completely (it is very important that the cake is cooled before pouring on hot syrup because otherwise it will turn mushy).
For the syrup: Mix all the ingredients together in a medium saucepan; bring it to a boil and boil for 5-7 minutes; remove cinnamon stick and pour hot syrup over cooled cake; let the cake cool completely (from the addition of the hot syrup) before serving.