Preheat oven to 350 degrees. Oil a standard loaf pan (8 1/2" x 41/2"). Cut a sheet of parchment to fit inside, with the long edges overhanging by a few inches, and oil the paper too.
Mix the ingredients for the chocolate swirl in a small bowl and set aside.
For the streusel, put the flour into a bowl and use a fork to blend with the butter until it's clumpy. Add the remaining ingredients and mix well. Set aside.
Stir together all the ingredients for the Pumpkin Bread in a mixing bowl until smooth. Scoop half the batter into the prepared pan. Distribute the swirl layer ingredients evenly over the batter.
Spoon the remaining batter over the swirl layer. Sprinkle the streusel over the top.
Bake the loaf 50 - 55 minutes, until a toothpick inserted in the center comes out with a few moist crumbs. Cool in the pan 30 minutes, then use the edges of the parchment to lift the loaf out of the pan. Place on a rack and cool completely.