Measure out one cup of whiskey and pour it into the blender.
Add half a cup of simple syrup to the blender, balancing sweetness with the whiskey's smoky notes.
Toss in two cups of ice cubes, filling the blender to achieve a thick, icy mixture.
Secure the lid on the blender and pulse a few times to start breaking down the ice.
Blend the mixture on high until the ice is finely crushed and the drink is smooth, about 30-40 seconds, making a thick, slushy consistency.
Check the texture; if desired, add more ice and blend briefly for a firmer slushiness.
Pour the whiskey slushie into chilled glasses, showcasing its icy, semi-frozen appearance with a golden hue.
Optionally, garnish with a twist of lemon or a sprig of mint for visual contrast and aroma.
Serve immediately with a spoon or straw, and enjoy the bold, icy burst of flavor.