In a large microwaveable bowl, add the stick of butter and the buttermilk or milk. Microwave for 1-2 minutes, until the butter is about halfway melted. Take it out and stir until the butter melts completely. 

Add the vanilla.

In a medium bowl, whisk together flour, sugar, baking powder, and salt.

Add the yolks to the wet ingredients and stir until combined.

Add the dry ingredients to the wet ingredients and stir gently. Don't overdo it! You want to stop mixing when you can still see a few streaks of flour. (Wipe out the dry bowl and put it back in your cupboard.)

Fold the egg whites into the batter. Do not over mix. Stir until it is barely incorporated, but make sure there are no giant lumps of dry ingredients or parts of the batter that look very soupy. 

If you are not eating these right away, or want to serve a group at the same time, heat your oven to 170 degrees F. (sometimes called "keep warm"). Place a cooling rack in your oven and put the cooked waffles on the cooling rack. This way they won't get soggy before you serve them.

I love serving waffles with oven fried bacon and scrambled eggs. Seriously, there is no better combo! Also, these waffles would be amazing topped with Cinnamon Honey Butter!

To reheat these waffles, use the toaster! These waffles also freeze beautifully. Double or triple the batch, throw the extras in a ziplock in the freezer, and have waffles any time you like. (Thaw on the counter and then toast.)