Wash the spinach thoroughly under running water and remove any thick stems. Peel the banana and slice it into smaller pieces if it is not already frozen. Measure all the ingredients so everything is ready to blend smoothly.

Pour the kefir into the blender first, followed by the spinach leaves. Add the frozen banana pieces, peanut butter, and honey if you want extra sweetness. Adding liquid ingredients first helps the blender mix everything more easily.

Blend the mixture on high speed for about 45–60 seconds until the smoothie becomes creamy and evenly blended. If the smoothie is thicker than desired, add a few ice cubes or a splash of kefir and blend again.

Pour the smoothie into a tall glass. Serve immediately while chilled and creamy. You can garnish with a sprinkle of chopped peanuts or a banana slice for extra presentation.