Pour the freshly squeezed lemon juice into the blender, ensuring you include any pulp for added texture.
Add the washed basil leaves to the blender, which will impart a bright, herbal note to the slushie.
Sprinkle in the granulated sugar or add honey to taste, then blend briefly to start dissolving the sweetener and releasing basil flavor.
Add the ice cubes to the blender, filling it nearly to the top to ensure a thick, icy consistency.
Secure the lid on the blender and blend on high until the mixture is smooth, icy, and has a slushy texture with tiny ice crystals visible.
Pour the vibrant, frosty slushie into glasses, and garnish with a small basil leaf or a lemon wedge for a decorative touch.
