To prepare the cake: Preheat the oven to 350° F. Butter the bottom and sides of a 9-inch springform pan, line with parchment paper and butter and flour the parchment paper.
Roast the almonds on a baking sheet for 5 to 7 minutes or until lightly browned. Place them in a blender or a food processor fitted with a steel blade and grind finely. While the almonds are roasting, remove the orange zest from the oranges with a zester or vegetable peeler and chop finely.
In a small bowl combine the almonds, orange zest, grated chocolate and cinnamon. Set aside.
In a large bowl beat the egg yolks until light and lemon-colored, incorporating as much air as possible. When the egg yolks are thick, add the sugar in two parts.
In another bowl beat the egg whites until stiff.
Beat the dry ingredients, orange juice and one-third of the egg whites into the egg yolks, then rapidly fold in the remaining egg whites. Pour the batter into the prepared pan and bake in the middle of the preheated oven for 35 to 40 minutes, or until the cake pulls away from the sides of the pan.
Loosen the sides of the pan and cool for 10 minutes. Invert the cake onto a rack to cool and remove the paper. When cool, paint with Grand Marnier.
To make the glaze: Break the chocolate into small pieces. In the top of a double boiler combine the chocolate, corn syrup and butter. Heat the pan and turn off the heat as the water comes to a boil. Beat with a whisk until smooth.
Place the cake on a rack over a pan or waxed paper and pour the glaze in the center. Tilt the cake to distribute the glaze evenly, and allow the cake to sit for 45 minutes before serving.
NOTE: The cake can be made up to a day in advance and should be kept at room temperature.