Well, you butter the bread on one side, put it in a skillet on medium heat, and place some chocolate on top. Once the chocolate starts to melt, spread it evenly over the bread with the back of a spoon. Spread peanut butter on the other slice of bread, and put the two slices together.
I'm using 100% dark, unsweetened chocolate because I'm worried I probably have gestational diabetes since my mom had it and I haven't been tested for it yet. Anyway, I sprinkle some xylitol on it for sweetness and use unsweetened peanut butter. I should probably be using whole wheat bread too, but at least I stick to breads with no high fructose corn syrup. I can't stand whole wheat bread; it tastes like cardboard to me.