Whisk the matcha. In a cup, add the matcha and 1–2 tbsp hot (not boiling) water. Whisk until completely smooth and frothy with a whisk or milk frother until there are no clumps.
Simmer the oats. In a pot, combine milk, oats, and a pinch of salt. Bring to a gentle simmer over medium heat, stirring frequently until thick and creamy (or desired texture), 3–5 minutes.
Stir in the whisked matcha, sweetener, and vanilla. Cook 30–60 seconds more—do not boil hard (this keeps the matcha vibrant and smooth).
Spoon into a warm bowl. Add desired toppings and enjoy!