Add dry ingredients to a large bowl and mix until evenly combined. Set aside.
To a smaller bowl, add eggs and egg whites and whisk until yolks are evenly incorporated. Add buttermilk, applesauce, brown sugar, and vanilla extract and whisk together. While continuing to whisk, slowly drizzle in the hot melted butter.
Add wet mixture into the dry mixture and whisk until just combined (I found that a large whisk works much better here than a fork, spoon, or spatula). It's okay if the mixture has lumps, so long as you can't see spots of powdery flour. Don't overmix it! This should be thicker than your average pancake batter. Allow the batter to rest for about 5 minutes while the griddle heats.
Pre-heat a griddle or griddle pan to medium-high heat (7 out of 10). You want it to be nice and hot before the first batch of pancakes goes down, then you'll turn it down slightly to medium heat (about a 5 or 6 out of 10).
Spray pre-heated griddle with non-stick cooking spray if needed (I didn't need it since my griddle was non-stick anyway). Using a 1/4 cup dry measuring cup, drop batter onto hot griddle to form 3-4" round pancakes. Once the pancake is bubbling on top and golden brown on the bottom, about 2-3 minutes, flip to cook on the other side. If you're planning to freeze the pancakes, set the cooked ones aside in a single layer on a cooling rack.
Once you've cooked the first batch of pancakes, turn the heat to medium (about 5 or 6 out of 10) and continue process until all batter is used up.