Cream butter and sugar together until smooth.
Gradually add the eggs and mix thoroughly for at least one minute. Then add 110g of plain flour and 1 and a half tsp of baking powder. Once the cake mix is smooth and combined, refrigerate it for at least one hour.
Now your mixture has rested, pre-heat your oven to 200C and spoon into your cases until half full (don't worry about the thick consistency of the mix it will spread and set once it is in the oven) Then take some blueberries and push them into each case (around 6-8 per muffin is fine) Bake for 20 minutes or until golden brown.
...And the final step...EAT AND ENJOY!