Pour the cooled coffee into the blender, giving it a gentle swirl to ensure it's evenly chilled.
Add the ice cubes to the blender, distributing them evenly across the surface of the coffee.
Secure the lid on the blender and pulse gently to start crushing the ice, listening for a hummed blending sound.
Blend on high speed until the mixture becomes smooth, frosty, and reaches a thick, slushy consistency—about 30 to 45 seconds.
Stop the blender and check the texture—if it's too watery, add a few more ice cubes and blend briefly again.
Pour the frozen coffee slushie into glasses, using a spoon or spatula if needed for a generous, inviting scoop.
Optional: garnish with whipped cream, a dash of cocoa powder, or a coffee bean for extra visual appeal.