01 - In a blender, add cold whole milk, chocolate ice cream, cocoa powder, chocolate syrup, and optional sugar.
02 - Blend on high speed until smooth and creamy, about 30 seconds.
03 - Taste and add more sugar or chocolate syrup if desired, then blend briefly again.
04 - Divide the milkshake evenly into two tall glasses.
05 - Top each glass with whipped cream and drizzle with additional chocolate syrup. Garnish with chocolate shavings or sprinkles if preferred.
06 - Serve immediately with straws.