After searching the net with no results, I'm hoping that someone in
here can help me. I'm looking to make a pumpkin loaf (or muffins) that
has a thick chocolate swirl running through it. Peet's coffee has this
as one of their pastry selections at their retail stores here in Los
Angeles. It's a thick slice of pumpkin loaf and there is this
wonderful, wide ribbon of chocolate batter layered within. Since I am
too calorie-conscious to usually buy coffee shop pastries, and all I
needed was the idea, I decided to try it on my own.

The pumpkin bread isn't so much the challenge.. it's the marbled
chocolate ribbon. I'm not sure how to create this for a loaf cake. I
want to use powdered cocoa, since I recently discovered the very real
and amazing difference that using Dutch Process cocoa makes compared
to regular cocoa and I'm excited to try it with different things.

Any help or suggestions would be greatly appreciated!