01 - Place mixed berries, sliced banana, milk, and water in a small saucepan.
02 - Heat over medium, stirring occasionally, until steaming hot but not boiling, about 3 to 5 minutes.
03 - Remove from heat and stir in honey or maple syrup, cinnamon, vanilla, and nutmeg if using.
04 - Transfer mixture carefully to a blender and blend on high speed until frothy and smooth.
05 - Taste and add more sweetener if desired, blending briefly to combine.
06 - Pour into mugs and enjoy immediately while warm.