Preheat the oven to 400. Spray a muffin tin with cooking spray, or line with paper liners.
In a medium bowl, whisk together the flour, sugar, salt, and baking powder. In a small bowl, combine the oil, egg, milk, and banana. Pour the wet ingredients into the dry ingredients, and mix until just combined.
Stir in the chocolate chips. Scoop the batter into the prepared muffin tin, filling nearly to the top. Sprinkle a few additional chocolate chips on the top of each muffin. Bake 15-20 minutes, or until lightly browned.