Peanut Butter Filling Cupcakes

I know it was a long time ago, but back in May I had this idea for making Reese's Peanut Butter Cupcakes. So I decided to try to make them, and came up with a recipe for a peanut butter and chocolate filling to add to the center of the cupcakes before baking them, and tried it out. Here're the cupcakes:

 

And here's how they look on the inside:

 

That darker spot is the filling. And while these tasted fantastic, they're not really what I had in mind at all, so I wasn't really satisfied with them. I was really hoping to make something that more resembled Peanut Butter cups, but I couldn't find peanut butter baking chips. I think I'll have to try to make these again some time so that I can get them right.

I'm also thinking that I'd like to avoid using too many more boxed cake mixes so that I can experiment with my own cupcake recipes. And maybe it would be good to focus on that particular basic before I moved on to other ideas...