Method

Batter:

Cream butter and sugar until light and fluffy, Color will change into off white.

Add one egg at a time then mix half the dry ingredients and half the liquids until well incorporated. Add in the other half of the ingredients and incorporate until the batter is smooth. Do not over mix. 

Gently mix the blueberries into the batter until well incorporated,

Place the mixture in a muffin cup and bake at 170C for 15 minutes or until an inserted toothpick comes out clean.