In a medium bowl, whisk together the sourdough discard, egg, milk, melted butter, and vanilla extract until smooth.
In a separate bowl, whisk together the flour, sugar, baking powder, baking soda, and salt.
Pour the dry ingredients into the wet ingredients and stir until just combined. The batter will be a bit thick. Do not overmix. If you prefer thinner pancakes, add a splash of milk to adjust the consistency.
Optional: For a long fermentation option, cover the bowl with plastic wrap and refrigerate for 12 to 24 hours before cooking. You can also cook the pancakes right away.
Heat a griddle or skillet over medium heat and lightly grease it with butter or oil. Scoop about ¼ cup of batter for each pancake onto the hot surface.
Cook for 2 to 3 minutes, until bubbles form and the edges begin to set. Flip and cook for another 1 to 2 minutes, or until golden brown.
Serve warm with butter, maple syrup, fresh fruit, or a drizzle of Old-Fashioned Hot Fudge Sauce for a special treat.