Step #1 In a large bowl, yogurt, sugar, banana, oil, beat eggs, & vanilla to mix.
Step #2 In a smaller bowl, stir this together whole-wheat & all-purpose flours, cinnamon, salt, cocoa, baking soda, & baking powder.
Step #3 Gently stir flour mixture & chocolate chips into egg mixture just until incorporated.
Step #4 Spoon batter evenly into 18 paper-lined muffin c (3/4-c capacity; fill them all the way to the top).
Step #5 Bake muffins in a 350° regular or convection oven until a wooden skewer inserted into the center comes out with moist crumbs attached, about 25 mins.