In a large bowl, whisk together the oat flour, baking powder and salt.
In a medium bowl, whisk together the Greek yogurt, eggs, melted butter, and milk. Add the wet ingredients to the dry and stir thoroughly to combine.
Let batter rest for 10 minutes (don't skip this step!)
Warm the waffle iron and when it is ready, scoop ¼ cup of the batter and place in the center of the waffle iron. Close lid and cook until done.
Repeat with the remaining batter to finish the batch; you may need to add a bit of milk if the batter becomes very thick. Waffles may be frozen or stored in the fridge for up to 5 days.
Notes
What setting for the waffles? I like to cook my waffles on the waffle iron's highest setting to make sure they are fully cooked inside and slightly crisp on the outside.
What size? I like to make my waffles using a ¼ cup measure, and a ⅓ cup measure also works well.
How long to cook the waffles? Cook the waffles until the light changes to green and there's no more steam coming off the top of the machine. This might mean you need to cook the waffles just a tad longer after the light changes. Add milk - Whole grain flour absorbs more liquid than all-purpose flour. You can add a little more milk, 1 tablespoon at a time if you find that the batter is too thick.
Make dairy-free - Make waffles dairy-free by substituting non-dairy butter for the butter, your favorite non-dairy milk for the milk, and non-dairy yogurt for the yogurt.
Swap coconut oil - Often, I will substitute the butter with unrefined or refined coconut oil for a change. The waffles are just as buttery and tender.
Add sugar - If you do want these waffles a bit sweeter, add 2 tablespoons of sugar to the dry mix.
Make egg-free - Substitute a flax egg for the egg.