Beat the butter, cream cheese and sugars on high speed until it's lighter in colour and fluffy. You can also use a whisk ;). Stop halfway through to scrape down the sides, so everything is nicely mixed.
Add the eggs and beat them on high speed again until they come together.
Add the milk and vanilla essence and mix them in.
Add the dry ingredients: flour, salt, baking powder, cinnamon. Mix them in as well. Don't overmix it though.
Fold in the blueberries using a spatula. If some of them are too big it's better to cut them up in half first.