Butter three 8 inch cake pans thoroughly and line the base of each with baking parchment. Rub a little more butter onto the paper. Preheat the oven to 350 degrees.

In a double boiler, melt the chocolate over simmering water, stirring occasionally, and set aside to cool. Sift the flour together with the sugar, baking soda, baking powder, and salt. In the bowl of an electric mixer or with a handheld mixer, beat the butter until it is fluffy. Add the flour mixture, 3/4 cup of the buttermilk, and the vanilla and beat in thoroughly, mixing for about 2 minutes with the electric mixer. Add the melted chocolate, eggs, and the remaining 1/4 cup of the buttermilk and beat for 1 minute longer. Pour an equal amount of the cake batter into each prepared pan and bake on the center rack of the oven for 30 to 35 minutes, or until a toothpick inserted into the center comes out clean. Cool the cakes in their pans for 15 minutes, then turn out onto a cake rack and finish cooling. With a soft pastry brush, brush any loose crumbs from the side edges of the cake layers.

To make the marmalade, combine the milk, sugar, egg yolks, and butter in a medium saucepan. Over medium heat cook the mixture, stirring constantly, until it thickens, about 10 minutes. Do not let the mixture come to a boil. Remove from the heat and add the coconut and pecans. Stir together well, then let cool almost to room temperature, beating occasionally so that it does not form a crust.

To assemble the cake, place the first layer of cake on a serving dish. Spread a layer of the marmalade on the top of the cake only, about 1/2 inch thick. Place the second layer of the cake on top of the first and spread the top of it with some of the marmalade. Finally, place the third cake layer on the top and spread a nice, thick, and slightly rounded layer of the marmalade on top of that. Cut into wedges for serving.