Best: Chocolate Banana Muffins

• 2 3/4 best basic muffin mix
• 2 1/2 natural bran
• 1 egg
• 700 gr all purpose flour
• 425 gr skim milk powder
• 300 gr granulated sugar
• 150 gr banana
• 120 gr chocolate chips
• 80 ml water
• 80 ml vegetable oil