Combine ¼ cup sugar and 1 tablespoon cinnamon in a small bowl.
Generously butter two loaf pans, then dust with the cinnamon sugar. Tap out excess and save for topping. Set aside.
In a mixing bowl, whisk the eggs into the starter, then whisk in the oil and rum. Add everything but the chocolate chips and whisk until blended.
Stir in 1 cup chocolate chips.
Divide batter between pans, then sprinkle remaining cinnamon sugar over the tops.
Sprinkle mini chocolate chips over the top and bake for an hour or until the bread loosens evenly from the sides and a toothpick inserted in the center of the bread comes out clean.
Cool in pans for 10 minutes, then turn out to cool completely on wire rack.