Peel the bananas and break them into chunks, then add them to your blender.
Scoop in the natural peanut butter, which should be warm enough to blend smoothly.
Pour in the milk, aiming for about 1 cup, and add any sweetener or vanilla if using.
Add a handful of ice cubes to the blender for a chilled, frosty texture.
Secure the lid and blend everything on high for about 30-45 seconds, until the mixture is smooth, creamy, and frosty.
Pause to check the texture—if it’s too thick, add a splash more milk and blend briefly; if it’s too thin, add a few more ice cubes or banana chunks.
Pour the smoothie into glasses, and optionally garnish with a drizzle of honey or a sprinkle of chopped nuts for added flavor and texture.
Serve immediately and enjoy the velvety, salty-sweet comfort in every sip.