Cook the Millet: In a small saucepan, bring the apple juice to a boil.
Stir in the millet, cover the pot, reduce the heat to medium-low, and let it simmer for 35 to 40 minutes. You're looking for a creamy, oatmeal-like texture.
Remove from heat and let it stand, still covered, for 5 minutes.
Transfer the cooked millet to a large bowl to cool for about 15 minutes.
Combine : Stir the freshly grated apple into the cooled millet.
In a separate bowl, whisk together the flour, baking powder, and salt.
Add this dry mixture to the millet and apple, stirring until just combined.
Finish the Batter: In a small bowl, whisk together the egg whites (or whole eggs), milk (or buttermilk), and melted butter. Gently fold this egg mixture into the millet batter. Be careful not to overmix; a few lumps are okay!
Cook the Pancakes: Heat a large skillet or griddle over medium heat and lightly coat it with vegetable oil. For each pancake, ladle about ¼ cup of batter onto the hot surface.
Cook for about 3 minutes per side, until golden brown and cooked through.
Serve and Enjoy: Transfer the cooked pancakes to a plate.
Repeat with the remaining batter, adding more oil to the pan as needed.
Serve warm with fresh fruit, a drizzle of maple syrup, or a dollop of yogurt.