Preheat oven to 360°F and grease a 9 x 5 inch baking tin.
In a medium mixing bowl, whisk together the all purpose flour, baking soda, salt, cinnamon, ginger, all spice, and cloves. Set aside.
In a small bowl, mix together the chopped chocolate, nuts, and 1 tsp of flour. Make sure that the chocolate and nuts are lightly coated with flour. This prevents them from sinking to the bottom of the batter.
Using a hand mixer or a stand mixer fitted with a paddle attachment, cream together the bananas and brown sugar in a medium bowl, until the bananas have broken apart. Small chunks of banana are okay.
Mix in the vanilla extract on slow speed. Beat in the eggs one at a time on slow speed until well incorporated.
Add the sourdough starter (or mix of milk and flour) and beat on slow speed until incorporated.
Add the dry ingredients, mixing on low speed until just incorporated. Be careful not to over-mix, as this can cause your bread to be tough. While the mixer is running, slowly pour in the milk and oil. The mixture will look a little chunky at first, but will smooth out after a minute or two.
Fold in the chocolate and nuts. Pour the batter into the greased tin and bake for 60 - 65 minutes until a toothpick pressed into the center comes out clean, with no batter. Melted chocolate on the toothpick is okay.
Remove from oven and let cool for 10 - 15 minutes.