Turn your waffle maker on to preheat.
In a large bowl, mix together flour, cheese, spinach, baking powder, garlic powder, and salt.
Add in the milk and melted butter, stirring until a thick batter forms (it will be thicker than pancake batter—don’t worry, that’s normal!).
Spray your waffle maker with oil or butter.
Scoop about 1/4 cup of batter into the waffle maker, close, and cook until crispy and golden brown.
Repeat with the remaining batter.