Putting a roof on a cake

[RockCrushesLizard]

I made a cake recently with a secret stash of M&Ms inside, for a surprise when it was cut. It was very simple, just a hollow inside the cooked cake, then assemble as normal. I discovered though, that they go soggy if left in a cake for too long.

My daughter has requested one of these cakes in the shape of a house for her birthday. My dilemma is how to avoid soggy sweets, without doing the whole thing on the day of the party, which would be horrendous!

I thought maybe I could make it hollow, decorate etc but leave the roof off until the day, then fill and attach the roof.

What could I make the roof out of though? Does gingerbread stick to cake? Tempered chocolate seems a bit high risk of breaking.

Any other ideas would be very welcome!

[moreismore]

Could you just make a separate sponge and then top with buttercream and maybe some biscuit roof tiles? Then fill and 'sandwich' the two together last minute?

[moreismore]

I'm thinking you could glue the biscuits upright for the roof shape...

[kingjofferyworksintescos]

Make it in advance with a chimney then just before you need it make a paper funnel and put the sweets inside ?

[Oblomov17]

Make your own Thin caramel sheet? Maybe with some nuts? If quite square, 2 bits would make a nice roof?

[RockCrushesLizard]

Good ideas!
I thought about keeping the top layer separate, but I was planning on windows etc, so I'm not sure I could get the sides looking good in time.
I am sadly crap at caramel - I've never yet managed it successfully.

The chimney idea is fab though - I would never have though of it!

[moreismore]

Chimney idea is genius-do that!