Does anybody have a tried and tested cupcake recipe that has a soft centre?

I have a wedding in Octobre and they want a cupcake tower. Since the top cake and the cupcakes will be iced in white with a little lilac here and there I want to make  a wow factor so that  when the cake is cut and people bite into the cupcakes the inside contrasts with the outside and is a surprise......any ideas or recipes? I have made a few try out with nutella and soft carmel but doesn´t matter what I do when I cut the cupcake in half there´s just a soft gooey mess in the bootom stuck to the paper lining........no wow factor. Any ideas?