Preheat the oven to 200 °C/400 °F (180 °C convection oven). Carefully grease the cups of the muffin baking pan or line with paper cups.
If using fresh blueberries, set aside 12 pretty berries for decoration. Drain blueberries from jar well in a collender. Remove 2 TBS. of liquid for the decoration. Please do not thaw frozen berries! If using fresh or frozen berries, crush a few berries for garnish.
In a medium bowl, thoroughly mix the flour with the baking powder, baking soda, rolled oats and blueberries.
In another large bowl, whisk egg lightly. Then add the sugar, vanilla sugar, butter or oil, sour cream and mascarpone and blend well. Add the flour mixture to the egg mixture and and stir just until the dry ingredients are moistened.