Preheat the griddle. (We like anywhere between 325°F and 350°F)
In a large bowl, whisk together the butter, eggs, milk, vanilla, and sourdough starter until combined.
Whisk in the remaining ingredients one at a time (the flour, baking soda, baking powder, and salt). The batter will be fairly runny. (It will puff up, don't worry!)
Once the griddle is hot, gently stir the pancake batter and use a 1/3 measuring cup to pour the batter onto the grill. (If the batter is too thick, add 1 teaspoon of milk at a time until you reach your desired consistency.)
Cook the pancakes for 2-3 minutes, and then flip them over, cooking them for 1-2 more minutes. Timing will depend on your griddle.
Serve warm with your favorite toppings.