I have been making a lot of choc-berry combination cakes at the moment. I think the two just go beautifully together. I think the big key is an excellent chocolate cake recipe, and further to that good ingredients.
The Chocolate cake I use is a chocolate sponge from Gorgeous Cakes by Annie Bell, and the cocoa I use is http://www.equagold.co.nz/ The quality of the cocoa is so important in chocolate cakes, so this one is premium dutch.
In all my recipes I have used the chocolate cake above, and then chose the tin I wanted to use.
The filling is Mascarpone (two packets), 2 punnets of berries (of your choice), raspberry powder http://www.fresh-as.com/foodservice/ and a little Te Horo raspberry jam.
If you want to make the filling into icing, just add a little icing sugar until it is the consistancy you would like.
Top with more berries and rose petals and you have a super cute and tasty cake!