Preheat oven to 425 degrees. Line a muffin pan with muffin liners or lightly grease with butter.
In a large bowl, Whisk flour, light brown sugar, granulated (or vanilla) sugar, baking powder, baking soda, salt, and cinnamon. Gently add in about half of the chocolate chunks, coating with the flour mixture. This will keep the chocolate from sinking to the bottom of the muffin. You will need 1/4 of the chocolate for the top of the muffins and will stir in the remaining chocolate in step 2.
Using a silicone spatula, stir in the bananas, oil, eggs, yogurt, buttermilk, and vanilla paste. Stir in 1/2 of the remaining chocolate. You should have about 1/4 of a cup of chocolate chunks left. Mix well until the flour is mixed in well with the batter. But- do not overmix- this will cause your muffins to become tough.
Using a large ice cream scoop, spoon the batter into the muffin liners until about 3/4 full. Top each muffin with remaining chocolate chunks- adding about 3- 4 pieces to each muffin.
Bake muffins at 425 degrees for 7-8 minutes, then LOWER the oven temperature to 350 degrees. Try NOT to open the oven door. Bake the muffins for an additional 12 minutes or until a cake tester inserted in the center comes out clean.
The tops will be rounded and just barely golden brown when done. Let the muffins cool for 5 minutes then transfer to a wire rack.