Add the milk, rolled oats, cinnamon, and salt to a medium saucepan.
Bring the mixture to a light simmer over medium heat, stirring occasionally.
Reduce the heat to medium-low and cook for about 5–7 minutes, stirring until the oats become creamy and tender.
Add 1 cup of blueberries during the final 2–3 minutes of cooking. If using frozen blueberries, add them directly and allow an extra 1–2 minutes if needed.
Remove the saucepan from the heat. Stir in the vanilla extract and maple syrup or honey. Add the optional butter for extra richness.
Divide the oatmeal between two bowls.
Top with fresh blueberries, Greek yogurt, chopped nuts, chia seeds, and an additional drizzle of maple syrup or honey if desired.
Serve warm.