In a large bowl, whisk together the sourdough discard, milk, egg, melted butter, and vanilla.
In another bowl, mix flour, sugar, baking powder, baking soda, and salt.
Add the dry ingredients to the wet mixture and stir until just combined.
Let the batter rest for 5–10 minutes to thicken slightly.
Heat a greased skillet or griddle over medium heat.
Pour about ¼ cup of batter for each pancake. Cook until bubbles form on the surface, then flip and cook until golden brown.
Serve warm with butter, syrup, or your favorite toppings.