Take a large glass (at least 16 oz) and fill it to about three-quarters full with ice cubes. Use standard-sized ice for best texture and cooling effect—approximately 2 to 3 minutes of chilling time.

Slowly pour 1 cup of cold brew coffee over the ice. The cold brew should hiss slightly as it hits the ice. Pour steadily to allow the coffee to cool evenly—this takes about 30 seconds to 1 minute.

Pour 1 cup of your chosen ready-made protein shake (vanilla, chocolate, or caramel) into the glass over the coffee and ice. Pour carefully to avoid excessive splashing—about 1 minute.

Stir the mixture vigorously with a long spoon or bar stirrer for 30 to 45 seconds until the coffee and protein shake are completely blended and the drink appears smooth and uniform in color.

Checkpoint: You are ready to move on when the drink is fully mixed with no visible separation between the coffee and protein shake layers, and the ice has begun to slightly soften the liquid.

Taste the proffee immediately and adjust sweetness or flavor intensity if desired by adding more protein shake or cold brew.

Serve immediately over the ice while still cold and frothy on top.