Using a blender, blend together the chocolate ice cream, half and half, and ⅓ cup of chocolate syrup. Blend just until combined.
Drizzle the chocolate syrup inside the milkshake glasses.
Evenly divide the milkshake between the 2 milkshake glasses.
Top with a thick layer of canned whipped topping.
Drizzle with the chocolate syrup and sprinkle with the chocolate sprinkles. Top with a maraschino cherry.
Notes
For the thickest milkshake, you should choose full-fat ingredients for this recipe.
You can also use heated hot fudge to drizzle inside the shake glasses.
Add a colorful straw and a long-handled spoon when serving your drink. Sip what you can and then scoop up the extra chocolate goodness with your spoon.