Prep your citrus. Zest the key limes first, then juice them.
Aim for about 2 tablespoons of juice and 1 teaspoon of zest. If using regular limes, start with 2 tablespoons and adjust to taste.
Load the blender. Add Greek yogurt, frozen banana, avocado, lime juice, lime zest, milk, honey, vanilla, and a pinch of salt to the blender. If you want a thicker, colder smoothie, add ice now.
Blend until smooth. Start low, then increase speed.
Blend for 30–45 seconds until creamy and uniform. Scrape down the sides if needed.
Taste and tweak. Want more zing? Add an extra squeeze of lime.
Need more sweetness? Add a bit more honey or maple syrup. If it’s too thick, splash in more milk.
Top like a pie. Pour into a chilled glass and sprinkle graham cracker crumbs on top.
Add a little extra zest for a pop of color and aroma.
Serve immediately. This smoothie is best cold and fresh, ideally within a few minutes of blending.