Heat up the waffle iron and brush with melted butter.
Combine all the ingredients (apart from the sour cream) together with 350 ml/11/2 cups water and stir to incorporate and form a smooth, thick batter.
Add a ladle of batter to the hot waffle iron. Close the lid and cook for 2–3 minutes or until golden brown.
Remove from the pan and serve immediately with sour cream if liked.