Heat an electric griddle to 350 degrees F or set a heavy skillet or griddle over medium heat.
Heat the oven to the lowest possible temperate (not more than 200 degrees).
Place the pancake mix in a large mixing bowl.
Whisk the egg whites and the buttermilk in a second bowl.
Whisk the egg yolks into the cooled melted butter (right in the pan in fine).
Whisk the butter mixture completely into the buttermilk mixture.
Dump the wet ingredients onto the dry ingredients and quickly bring together with a large whisk. (12 stirs ONLY, then just walk away! Yes, there will be some lumps in the batter and that's fine.)
Check on the griddle. When a drop of water skittles across the surface like a little hovercraft, it’s ready. If you’re surface is truly non-stick, no butter or non-stick spray will be needed.
Ladle 2 tablespoons of batter onto the griddle. (Or, use a #20 disher, or a 1-ounce ladle.)As soon as the batter hits the pan, gently coax the batter out to a disk about 4 inches in diameter. Cook for 3 minutes, or until bubbles around the upside edge set. (If you're adding fruit into the pancake itself, add it after the batter has been on the griddle for about 30 seconds.)
Carefully flip with a wide spatula, and cook for another 2 to 3 minutes, until golden brown on the bottom.