Preheat the oven to 350f/175c Grease a 9-inch spring-form pan and set aside.
In a small heat-safe bowl, soften the butter and cream cheese together in the microwave until very soft, but not completely melted (don't worry if some of the butter melts).
Mix all the wet ingredients and sugar with the cream cheese mixture until combined. Mix in the remaining dry ingredients by hand.
Fold in the blueberries (reserving some of them for after the batter is added to the pan).
Add the batter evenly to the pan and then place the blueberries evenly across the top of the batter.
Bake for 55-65 minutes or until a cake tester comes out clean, and when gently pressed, the middle of the cake should feel firm & springy. If the cake starts to brown too much cover in foil and return to the oven.
Let cool in the pan for 5 minutes before removing from the pan and transferring to a wire rack.
For the icing:
In a mixing bowl whisk together the butter, cream cheese, powdered sugar, and vanilla extract.
Add the milk as needed 1 tablespoon at a time until it is the desired consistency.
Once the cake has cooled, drizzle with the icing and serve.