Butter and flour an 8 by 2 inch round cake pan, then line with parchment paper.
Melt the butter and chocolate in a small, heavy saucepan, over low heat, stirring until smooth. Transfer the chocolate to a large bowl and mix in the sugar, orange zest and Grand Marnier.
Let cool 5 minutes.
Stir in the eggs, one at a time, and blend thoroughly. Stir in ground walnuts.
Pour the batter into the prepared pan and bake for 25 minutes.
The cake should feel soft but not liquid when gently pressed in center. Do not over bake.
Let cool 15-20 on a wire rack before releasing the cake from the pan.
Release the cake from the pan, peel off the parchment paper and discard. Finish cooling.
Put the chocolate and butter in a 1 quart glass bowl and microwave in 30 second increments, stirring in between until smooth and shiny. Gently stir in the honey.
Invert the cake onto a cardboard round, and if you have one, on a decorator’s turntable.
Using a metal icing spatula, apply a thin coating of the glaze over the top and sides of the cake. Allow to cool.
Place the cake, on the cardboard round, onto a wire rack over a rimmed baking sheet.
Pour the glaze onto the center of the cake, and gently tilting the cake let the glaze flow over the top and sides of the cake. Set the cake on a serving plate and once cooled place the 3 walnut halves in the center in the form of a triangle. Drizzle with chocolate and serve.