Add the frozen vanilla ice cream, milk, vanilla extract, and ice cubes into the blender.
Secure the lid and blend on high speed until the mixture is smooth, thick, and frosty, about 30-40 seconds. You should see a creamy, slushy consistency emerge.
Pause the blender briefly to check the texture; if it’s too thick, you can add a splash more milk and blend again for a few seconds.
Once blended to your desired smooth and icy texture, turn off the blender.
Pour the vanilla slushie into glasses, spooning any remaining mixture for those who love extra creamy bits.
Serve immediately with a straw or a garnish if desired, and enjoy the refreshing, smooth texture of this simple vanilla treat.