Add the matcha powder to your cocktail shaker or mason jar. Sift the matcha through a fine mesh strainer if you notice any clumps, as this will ensure a smooth, lump-free drink just like McDonald's version.
Pour the hot water over the matcha powder in the shaker. Using a small whisk or by shaking vigorously, mix until the matcha is completely dissolved and the mixture turns into a smooth, vibrant green liquid with no visible powder clumps, about 30 seconds of whisking or 15 seconds of shaking.
Add the vanilla syrup to the matcha mixture and stir or shake again to combine thoroughly. The syrup should blend seamlessly with the matcha, creating a sweetened green tea base that smells fragrant and slightly vanilla-scented.
Fill your tall serving glass with ice cubes, filling it about three-quarters full. The ice should reach near the top of the glass to ensure your drink stays cold and refreshing throughout.
Pour the cold milk over the ice in the glass. The milk should fill the glass leaving about an inch of space at the top for the matcha mixture.
Slowly pour the prepared matcha mixture over the milk and ice. You'll notice the vibrant green matcha cascading through the white milk, creating beautiful layers before mixing together.
Using a long spoon or straw, gently stir the drink from bottom to top to combine the matcha with the milk. Continue stirring until the drink turns a uniform light green color throughout, indicating the matcha is evenly distributed.
Serve immediately with a straw and enjoy your homemade McCafé-style iced matcha latte. The drink should taste creamy, slightly sweet, and have the distinctive earthy matcha flavor that makes the McDonald's version so popular.
