In a blender, add 500 ml of chilled milk, 4 scoops of butterscotch ice cream, and 2 tablespoons of butterscotch sauce. Blend until smooth and creamy.
Pour the shake into 2 tall glasses, leaving some space at the top.
Top each glass with a scoop of butterscotch ice cream and drizzle with 1 tablespoon of butterscotch sauce.
Garnish with crushed butterscotch chips or praline, and serve immediately with a straw and a long spoon.