In a small pot, whisk together the milk, egg, sugar, vanilla, and a pinch of salt until smooth.
Place the pot over medium heat and stir gently until the mixture begins to warm.
Add the oats and cook, stirring often, until the mixture thickens into a creamy consistency.
Sprinkle with cinnamon and adjust sweetness as desired.
Serve warm with your favorite toppings like fruit, nuts, or a spoonful of jam.