Brew and cool your coffee. Make it strong so the flavor stands out. Cool it in the fridge, or pour it into an ice tray to make coffee cubes.
Add liquids first. Pour the cooled coffee and milk into the blender. This helps the blades catch the solids better.
Layer in the dry ingredients. Add oats, protein powder, chia or flax, cinnamon, and a pinch of salt.
Add the creaminess. Drop in the frozen banana and nut butter.
If you like it extra cold and thick, add a few ice cubes.
Sweeten to taste. Start with no added sweetener if your protein powder is sweetened. If needed, add maple syrup or a date.
Blend until silky. Start low, then increase to high for 30–45 seconds. You want a smooth, creamy texture without oat grit.
Taste and tweak. Too thick?
Add a splash more milk. Too thin? Add a bit more banana or a few more ice cubes.
Serve right away. Pour into a tall glass or a to-go cup.
Top with a sprinkle of cinnamon or a few crushed oats if you like.