Preheat oven to 350 degrees and line muffin tins with paper liners. Whisk dry ingredients in a bowl and set aside.
In a blender, blend oil, milk and spinach on high until completely puréed. Then add mashed banana and vanilla and blend again.
Pour puréed mix into dry mix and fold together with a rubber spatula until completely combined.
Fill muffin cups and sprinkle some chopped pistachio nuts on top of each. Bake 18-20 minutes or until toothpick inserted to the center comes out clean.