Let the chocolate ice cream sit at room temperature for 3-4 minutes to soften slightly. This helps create a smoother blend without needing excess liquid.
Add the ice cream, milk, malted milk powder, chocolate syrup, and vanilla extract to a blender in that order. Starting with ice cream on the bottom helps the blades catch better.
Blend on low speed for 10-15 seconds, then increase to medium speed. Blend until just combined and smooth, about 20-30 seconds total. Over-blending creates a thin, airy texture instead of thick and creamy.
Check the consistency by lifting the blender lid. The shake should be thick enough to slowly pour but not so thick it won't move. If too thick, add 1 tablespoon of milk at a time and pulse to combine.
Pour immediately into chilled glasses. Use a spatula to scrape down the sides of the blender to get every last bit.
Serve right away with a wide straw and optional toppings like whipped cream, chocolate shavings, or crushed malted milk balls.
