Mix dry ingredients together (2 cups flour, 1/2 cup sugar, 2/3 cup brown sugar, 2 teaspoon baking powder, 1/2 teaspoon baking soda, 1/2 teaspoon salt). Set the bowl aside.
Mash 3 bananas up with a potato masher. Add in 2 eggs, 1/2 cup Greek yogurt, 1/3 cup vegetable oil, and 1 teaspoon vanilla. Mix together until well combined.
Add the dry ingredients to the wet ingredients and stir until just combined. You don't want to work the batter too much.
Gently fold in the chocolate chunks so they are evenly distributed throughout the batter.
Allow the batter to rest at room temperature or in the fridge for 30 minutes to one hour.
Preheat oven to 425F.
Fill a muffin tin with liners in every other hole, and spray liners gently with oil. See Note 2.
Fill muffin liners with batter almost to the top.
Place a few extra chocolate chunks on top of each muffin (makes a nice decoration)
Place in the oven at 425F for 7 minutes. Lower heat to 350F and continue baking for 15-20 minutes until tops are brown and muffins are fully baked. See Note 3.
Allow to cool in pan for 5 minutes.
Remove muffins and finish cooling on a cooling rack
Serve warm or at room temperature.