Toffee Crunch Muffins

• 3 bars chocolate cover toffee
• 1 egg
• 190 gr all purpose flour
• 120 ml milk
• 120 ml dairy sour cream
• 75 gr firmly packed brown sugar (light)
• 45 gr butter
• 9 gr baking powder
• 4 gr vanilla extract
• 2 gr baking soda