Add the vanilla ice cream, milk, ice cubes, sugar, and vanilla extract into your blender.
Secure the lid and blend on high speed until the mixture is smooth yet thick and icy, resembling a slushie texture. This usually takes about 30-45 seconds.
Check the consistency; if it's too thick, add a splash more milk and blend briefly again. For a chunkier texture, add a few more ice cubes and pulse gently.
Once the slushie has a creamy, icy consistency, turn off the blender and give it a gentle stir to ensure an even texture.
Pour the slushie into chilled glasses, allowing some to fizzle over the edges for a fun, frosty look.
Serve immediately with a straw or spoon, and enjoy the refreshingly thick experience of a frozen milkshake treat.