In a large bowl, combine the flour, baking powder, salt, and sugar.
In a blender, pour the milk, egg, butter, and spinach. Blend on high speed until smooth.
Pour the green mixture into the flour bowl and with a whisk or fork, mix from the outside of the bowl in to combine, until all the visible lumps are gone.
Cook the pancakes:
Heat a non-stick griddle or large pan over medium-high heat. Once hot, grease it with oil or butter. Immediately pour or scoop ¼ cup of batter for each pancake. Cook the first side for about 2 minutes, until the edges look defined and bubbles have formed throughout. Flip the pancakes over and cook for one more minute. Remove from the pan onto a plate and repeat with the remaining batter.
Serve:
Stack them high and top with your favorite toppings and syrups.
Notes
Use the right baking powder: Since pancake batter naturally has a mild, neutral flavor, it's important to use aluminum-free baking powder. The metallic flavor will ruin the taste, especially in fluffy pancake recipes that call for 2 or more teaspoons. Trust me on this one.