that might be good after baking, but i during epi making the mozz would flow out during the bake probably...
i have always wanted to make an epi, but after watching it done, i decided to keep the length natural, just because my wife loves tearing bread apart..
I think if you were to take an oiled knife and make a slit in the top of each section and put in a slice of mozzarella and the garlic butter that way it should work quite well. I'd even be tempted to put a sun dried tomato in there too, I really should have a go at this