Preheat oven to 350 degrees. Line standard muffin tins with paper liners.

Whisk together the flour and baking powder and sift; set aside.

Paste the banana with a kitchen mixer and set aside until use.

Cream the butter and brown sugar. Add the eggs gradually; stir until well mixed (emulsification). Add the banana paste and stir until smooth.

Add the flour mixture and chocolate chips to the butter mixture and use a rubber spatula to mix until smooth.

Divide the batter evenly among the lined cups.

Bake for 20(+6) min, rotating the tins halfway through. Transfer tins to wire racks to cool completely before removing the muffins.

More Details at http://www.chez-k.org/english/muffins/banana-chocochip-muffins/