Brew and chill the coffee. Make a strong cup and let it cool.
For best results, use cold-brew or refrigerate hot coffee until cold.
Load the blender. Add milk, chilled coffee, frozen banana, cocoa powder, nut butter, vanilla, salt, and any protein powder or optional add-ins.
Adjust sweetness. Taste your banana first. If it’s not very ripe, plan on adding a bit of sweetener.
Blend until smooth. Start low, then increase to high for 30–45 seconds. Scrape down the sides if cocoa clings to the pitcher.
Add ice for thickness. Blend in 1/2 cup ice.
If you want it thicker, add more a little at a time until it’s milkshake-thick.
Taste and tweak. Add a little more cocoa for deeper chocolate, a splash more coffee for stronger mocha, or sweetener if needed.
Serve immediately. Pour into a chilled glass and, if you like, top with cacao nibs or a dusting of cocoa.