Slice the avocado in half, remove the seed, and scoop out the flesh.
Rinse your kale and mint thoroughly.
Slice the cucumber and fennel (or celery) into smaller pieces.
Add all ingredients to a high-speed blender.
Blend on high until the smoothie is creamy and fully combined.
If needed, adjust thickness with more almond milk or ice.
Pour into glasses and enjoy immediately for maximum freshness.