Combine chilled coffee, avocado, almond milk, a scoop of Perfect Keto Unflavored Keto Collagen, cocoa powder, ½ cup ice cubes and erythritol (if using) and blend until smooth.
Fill the glass or mason jar with remaining ice cubes, pour coffee-collagen mixture over the ice.
Garnish with a pinch of cinnamon and crushed chocolate (optional) and serve.