Add the vanilla ice cream, ice cubes, milk, and vanilla extract to a blender.
Blend on high speed until the mixture is smooth and the ice is fully crushed, about 30-60 seconds. You should see a frosty, creamy texture forming.
Stop the blender and check the consistency—if it's too thick, add a splash more milk; if too thin, add a bit more ice and blend again.
Pour the slushie into glasses, watching as it retains a thick, icy texture with a smooth appearance.
If desired, top with whipped cream or garnish with a vanilla bean for added aroma and visual appeal.
Enjoy immediately with a straw or spoon for a cool, creamy treat with a frosty finish.