In a blender, add 500 ml of cold milk, 4 scoops of chocolate ice cream (about 200 grams), and 2 tablespoons of unsweetened cocoa powder.
Blend the ingredients together until smooth and creamy. If you prefer a thicker milkshake, add more ice cream and blend again.
Pour the milkshake into two tall glasses and garnish with whipped cream and chocolate shavings or chocolate syrup, if desired.
Serve immediately with a straw and enjoy your delicious chocolate milkshake.