Nutty Chocolate& Mashmallow Muffins

• 1 egg
• 240 ml sour cream
• 190 gr flour
• 110 gr melted marg
• 110 gr brown sugar
• 100 gr marshmallows (chopped)
• 60 gr walnuts
• 34 gr cooking chocolate melted
• 5 gr baking powder
• 4 gr vanilla