Banana Oatmeal Muffins

• 2 bananas (chopped)
• 1 egg (beaten)
• 3/4 brown suger packed
• 240 ml buttermilk
• 160 gr rolled oats
• 130 gr all purpose flour
• 55 gr butter
• 14 gr baking powder
• 1 gr salt
• 1 gr allspice