Banana Raisin Walnut Muffins Ww

• 1 egg (lightly beaten)
• 1 bananas ripe
• 240 ml buttermilk (plus)
• 130 gr flour (plus)
• 120 gr nonfat dry milk powder
• 85 gr golden raisins plumped
• 55 gr brown sugar firmly packed
• 60 ml vegetable oil less
• 28 gr whipped butter melted
• 14 gr walnuts (chopped)