Gather and prep your ingredients. Pull the sourdough discard from the refrigerator, melt the butter and let it cool slightly, and have all other ingredients measured and ready.
In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, baking powder, baking soda, and fine salt until well combined. Make a well in the center.
In a separate medium bowl, whisk the sourdough discard to loosen it. Add the egg, milk, cooled melted butter, and vanilla extract. Whisk until fully combined and smooth.
Pour the wet ingredients into the well of the dry ingredients. Gently fold together with a rubber spatula using slow strokes until just combined and no dry streaks remain. A few lumps are okay.
Let the batter rest for 3 to 5 minutes while you preheat your griddle or skillet over medium-low to medium heat.
Grease the preheated griddle with a small pat of butter, swirling to coat the surface evenly. Test the heat by flicking water onto the surface.
Using a 1/4-cup measuring cup or ladle, pour batter onto the griddle, spacing pancakes at least 2 inches apart. Cook until bubbles form across the top and the edges look set, about 2 to 3 minutes.
Flip gently with a flat spatula and cook the second side for another 1 to 2 minutes until golden brown. Transfer to a wire rack in a warm oven while you finish the batch.
Stack pancakes on warm plates, top with maple syrup, fresh berries, and any other desired toppings. Serve immediately while hot.