I have made number cakes twice now, once a 40 for my husband, and a 97 for my Grandma.
I used these large silicone moulds* both times, and as long as they are well-greased the cakes turn out really well.
The 97 cake, it was for a big family party, so there was a mix of children and adults. So I decided to do the 9 in chocolate sponge, with chocolate icing for the children, and filled the top with flakes, smarties, buttons, and Maltesers. The outside of the cake had chocolate fingers all around it too.
The 7 was a classic vanilla sponge, white fondant icing to cover it, and then purple flowers covering it.
To cut the flower shapes I used these fondant tools* that have flower cutters in different sizes.
The 40 cake was ALL chocolate!
I used every different kind of chocolate I could buy to cover it.
And the effect is brilliant and really easy to do as there is nothing intricate about it!