Here's the recipe:
Take a bowl big enough to hold as many chicken breasts as you're making for the evening. Pour in coconut rum to almost cover them, and add a dash of Worcestershire. I probably use about 10% Worcestershire, or a bit less. Then add black pepper. For 6-8 chicken breasts I'd guess I add about two teaspoons of black pepper, adjusted up or down depending on how long they'll be marinating, and optionally about a teaspoon of white pepper. The longer you marinate them, the less pepper you use -- it really soaks in, and it can get *very* strong over a full day of marination. The amount above is good for about three hours of marination. The coconut rum will soak in properly in about an hour, it's the other components that take time.
Ordinarily I'll then chop up some mango or apple (don't use kiwi, pineapple or other very acidic fruit! If the Jell-O box says not to use it, don't use it for this!). I mix the chopped fruit with ricotta cheese, stuff the mixture into the chicken breasts, and bake at 275 for about an hour.
However, this time I mixed things up a bit. I cooked the chicken breasts without the fruit-and-ricotta mixture (same time, same temperature) and diced them into 3/4" cubes. I also pureed some blackberries, pretty coarsely so that there were one or two berries mostly whole, and the seeds were intact. I made some basic crepes. I filled each crepe with diced chicken, blackberry puree and ricotta, then folded it to keep the puree from leaking.
Overall, it worked pretty well. The ricotta added the creaminess I was looking for, but was a bit too strong. Next time I'll probably mix it with chevre or something to keep it from overpowering the fairly subtle rum flavor. Cooking it in the chicken does this well, but I'm not sure how to get the same effect without baking it.
Alternately, I could bake it in the chicken like before and dice it along with the chicken. That'd balance the flavors nicely. I'll probably need to tone down the blackberry flavor somehow if I do that, but that's a good idea anyway.
If I make the recipe more complicated later, the obvious thing to do is something with the blackberries. Puree is all well and good, but the strength and tartness is a little much with the chicken. Cooking the puree with lemon juice, simple syrup and/or butter are classic ways to tone it down and make the flavor more complex. I'll try that next time if I'm feeling elaborate. I could also choose a less assertive fruit like papaya, which would be less likely to overpower the chicken-and-rum.