Slice bananas and add to a freezer-safe container or a lay on baking sheet. Add to freezer and leave at least 3+ hours, can be left overnight.
Add frozen bananas together with milk to a blender and blend until chunky and mixed.
Once ice cream is almost smooth, add in nut butter or any powdered optional ingredients and blend until smooth.
Optional: if have an ice cream machine, slow churn mixture for a less grainy ice cream texture.
Finish by mixing in any solid optional ingredients, or swirling in extra nut butters or spreads and transfer to a freezer-safe container.
Freeze until solid, approx. 2-3 hours, and serve fresh, topping with fresh bananas or other toppings.