Soften the butter at room temperature and then smash energetically (get help from a food processor) together with sugar for a few minutes until the mixture turns creamy.
Place the paper cups in the 6 muffins tray.
Put the mixture into cups (fill up to the edge), sprinkle the surface with some blueberry and place them in a preheated oven at 180 ° C for about 20-25 minutes.
After baking, the muffins will be golden on the surface, then turn off the oven and let it rest there for 5 minutes with open door, then pull out and let it cool down completely.
Remove the paper cups from the tray and decorated with the remaining blueberries.