Add all ingredients with the exception of the agave syrup to the blender and blend on high until smooth and creamy. If needed, scrape sides with spatula midway through blending.
If your smoothie is too thin, add a little more milk, a tablespoon at a time until desired consistency is reached.
Blend in agave syrup until desired sweetness.
Pour into a large glass. Garnish with additional berries and serve immediately.