Place the frozen blueberries into the blender pitcher, ensuring they are evenly distributed at the bottom.
Add the crushed strawberries into the blender, layering them on top of the blueberries.
Secure the lid on the blender and puree on high speed until the mixture is smooth and thick, about 30-40 seconds. You should see the ingredients fully combined with a glossy, slightly pulpy texture.
Stop the blender and check the consistency; if desired, add a little more milk and blend briefly to thin slightly. The final blend should be uniformly colored with visible small fruit chunks and a smooth surface.
Pour the smoothie into serving glasses, and optionally garnish with a few whole berries or a slice of strawberry for presentation.