In a large bowl, mix sourdough starter, flour, sugar, baking powder, baking soda, and salt.
Add milk, egg, and melted butter to the dry ingredients.
Stir until just combined; the batter may be slightly lumpy.
Let the batter rest for 10 minutes.
Heat a skillet or griddle over medium heat and grease lightly.
Pour 1/4 cup of batter onto the skillet for each pancake.
Cook until bubbles form on the surface, about 2-3 minutes.
Flip and cook for another 2-3 minutes until golden brown.
Remove and keep warm while cooking the remaining pancakes.
Serve with your favorite toppings.