In a mixing bowl, combine the sourdough discard, all-purpose flour, sugar, baking powder, baking soda, and salt. Whisk together until there are no dry flour pockets.
In a separate bowl, whisk together the milk and egg until combined. Then add the melted butter and mix well.
Pour the wet ingredients into the dry ingredients. Stir until just combined; don’t overmix; a few lumps are okay.
Heat a non-stick skillet or griddle over medium heat and add a little butter or oil to coat the surface.
Pour about ¼ cup of the batter onto the skillet for each pancake. Cook until bubbles form on the surface and the edges look set, about 3-4 minutes.
Flip the pancakes and cook for an additional 2-3 minutes until they are golden brown.
Repeat with the remaining batter, adding more butter or oil as needed.
Serve warm with your favorite toppings like syrup, fruit, or yogurt.