In a small bowl, sift the matcha powder to remove any clumps. Add hot water and stir vigorously until smooth and frothy. Pour into a cup.
In a small saucepan, warm the milk over medium-low heat, stirring occasionally, until hot but not boiling.
Optional: If you have a frother, froth milk until creamy.
Pour milk into the cup with the matcha mixture.
Top with whipped cream or marshmallows, and dust with matcha for an elegant finish.