In a large mixing bowl, sift together the all-purpose flour, granulated sugar, baking powder, and salt. Sifting ensures that the dry ingredients are well combined and free of lumps, providing a smooth batter for your pancakes.
In a separate bowl, whisk together the milk, egg yolks, melted unsalted butter, and vanilla extract until well combined. Ensure the butter is cooled to avoid curdling the mixture.
Gradually pour the wet ingredients into the dry ingredients, stirring gently until just combined. It's important not to overmix; a few lumps are okay to maintain the batter's fluffiness.
In a clean, dry bowl, use an electric mixer to beat the egg whites until stiff peaks form. This step is crucial for achieving the soufflé-like texture of the pancakes.
Carefully fold the whipped egg whites into the pancake batter in three additions. Use a gentle folding motion to preserve the airiness of the egg whites, ensuring a light and fluffy pancake.
Heat a non-stick skillet or griddle over low to medium heat and lightly grease with butter or oil. Using a ring mold, pour approximately ¼ cup of batter into each mold. Cover the skillet with a lid and cook for about 4-5 minutes until bubbles form on the surface. Carefully flip the pancakes and cook for an additional 3-4 minutes until golden brown and cooked through.
Gently remove the pancakes from the molds and stack them on a serving plate. Top with a drizzle of maple syrup, fresh berries, a dusting of powdered sugar, and a dollop of whipped cream if desired. Serve immediately while warm and airy.