Although I had never made anything similar, when asked to make a coffin-shaped cake for Going-Away party on Halloween, I said yes, and figured it out. The invitation was Victorian in style, black and silver.
The 12x18 cake was devil's food (appropriately), with coffee flavor, soft caramel, vanilla buttercream covered with chocolate fondant. Putting the fondant on the cake was terrifying, I have never covered a cake that large, so I had to MacGuyver it together and cover my mistakes with a large fondant ruffle around the edge. I have a die-cutting machine (called a Cricut Cake) that I used to make the white flourishes, which I then covered in silver luster dust (like eyeshadow, but food safe). Around the edges, I stamped silver cobwebs and spiders.
The guests of honor seemed very happy with the cake, and the reviews were positive. I have already been contacted by one of the party-goers for another cake.
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Chouquette Coffin Cake