01 - Melt butter in a small skillet over medium heat, swirling occasionally until golden brown and fragrant, about 3–4 minutes. Transfer to a heatproof bowl to cool slightly.
02 - Place blueberries, oats, banana, milk, yogurt, honey or maple syrup, vanilla extract, and salt in a blender.
03 - Pour the cooled brown butter into the blender with the other ingredients.
04 - Include ice cubes for a colder, thicker texture if desired.
05 - Blend on high speed until fully smooth and creamy, about 1–2 minutes.
06 - Taste and add more sweetener if needed.
07 - Pour into glasses and serve immediately.