In a large mixing bowl, combine the flour, sugar, baking powder, baking soda, and salt. Whisk together until well blended.
In a separate bowl, mix the sourdough discard, egg, milk, and melted butter until smooth. Make sure the mixture is at room temperature for the best results.
Pour the wet ingredients into the dry ingredients and gently fold them together until just combined. Be careful not to overmix; a few lumps are okay.
Heat a non-stick skillet or griddle over medium heat and lightly grease it with butter or oil. Once hot, pour about 1/4 cup of batter onto the skillet for each pancake.
Cook the pancakes for 2-3 minutes or until bubbles form on the surface and the edges look set. Flip the pancakes and cook for an additional 1-2 minutes until golden brown and cooked through.
Remove the pancakes from the skillet and keep them warm in a low oven while you repeat the process with the remaining batter.