Next week I will be making a cake that is part vanilla and raspberry, part chocolate and I'm looking for some fresh ideas to use as fillings between the layers that won't shorten the shelf life of the cake.
I usually tell people to eat the cake within a week from delivery, and I usually allow myself about 3 days to ice (during which time the cake is kept at room temperature) - so I'm looking for a 10-14 day shelf life.
Normally with a raspberry filling I add fresh raspberries to raspberry jam, which gives the jam a sharper taste which I prefer. I think the jam helps preserve the fresh raspberries - they always seem to last until the cake is eaten - but I'm not sure and would would welcome your views on this, and any alternative suggestions.
At home when I make chocolate cake, I like to use a light buttercream or cream cheese filling, but I'm pretty sure this won't keep, so for clients I often layer chocolate cake with a chocolate spread like Nutella, but personally I find this makes the cake too cloying and heavy in the mouth. So I really would appreciate any ideas for a light, long-lasting filling for chocolate cake.
I'm in the UK, so we don't get a lot of the branded products you have in the US, so if these can be avoided so much the better.