Gather all your ingredients.
Prepare the green smoothie base by blending fresh spinach until smooth.
Mix dry ingredients: flour, cocoa powder, baking powder, baking soda, and salt in a medium bowl.
Combine wet ingredients: granulated sugar, brown sugar, applesauce, milk, vegetable oil, and vanilla extract in a large bowl.
Add spinach puree to the wet ingredients and mix until fully incorporated.
Gradually add dry ingredients to the wet mixture and stir gently until just combined. Fold in chocolate chips.
Preheat oven to 350°F (175°C) and fill muffin tins with batter, filling each about 2/3 full.
Bake for 18-20 minutes or until a toothpick comes out clean. Cool in the pan for 5 minutes before transferring to a wire rack.