These stacks are so fluffy and flavorful, you'll never make pancakes the traditional way again. The acidity in the orange juice helps boost the baking soda's power for an airy texture, and its flavor complements the vanilla.
Whisk together the orange juice, butter, vanilla, egg yolks and 3/4 cup room-temperature water in a medium bowl until well combined. Whisk together the flour, sugar, baking powder, salt and baking soda in a large mixing bowl. Stir the wet ingredients into the dry just until incorporated.
Whisk the egg whites in a separate large bowl with an electric mixer until stiff peaks form. Add the egg whites to the batter and fold them in gently, being careful not to deflate them too much.
Heat a large nonstick skillet over medium heat. Spray the skillet with nonstick cooking spray, then add about a heaping 1/4 cup of the batter. (If you can fit 2 pancakes at a time go for it, but don't crowd the skillet too much; they will take longer to cook and will be harder to flip.) Cook until bubbles form all over the surface and begin to pop, about 2 minutes. Flip and cook until cooked through, another 1 to 2 minutes. Remove to a baking sheet and keep warm in the oven. Continue with the remaining batter.
The orange juice adds great flavor and a little extra boost to the leavening, but if you don't have any, you can use water instead.