Combine flour, baking soda, baking powder, salt. Set aside.
In a large bowl whisk milk, eggs, sugar, vanilla. Hold back a bit of the milk to see if you'll need the entire amount. In the end, the batter should be the consistency of thick cake batter.
Add the stirred down sourdough starter.
Fold in the dry ingredients and gently stir to combine. Try to fully incorporate but not over-mix.
As mentioned above, look at the consistency of the sourdough batter, it should drip off the spatula in a thick slow stream, if it's still too thick and not in a heavy drip, add more of the milk to get it to that point. My batches usually require around 1 1/2 cups milk, sometimes a few tablespoons more. I've included a video so you can see how it should look.
Allow the batter to rest for 20 minutes. You'll see small bubbles start to appear here and there.
Heat your griddle between 325-350f or a non-stick frying pan over medium to med-high heat. Use oil, butter, or ghee to grease the griddle. I like ghee (clarified butter) or a combo of melted butter & oil. The ghee will give that crispy edge and gorgeous varied color.
Using a measuring cup, scoop 1/2 C of pancake batter onto the hot griddle.
Monitor for some bubbles to appear in the sourdough pancake, then flip. Adjust your heat as needed. The pancake will rise a bit on the first side, but will rise even further after flipping it over.
Serve fresh off the griddle or warm over in a 200f oven if needed.
If using blueberries, you can either mix them into the batter as the final ingredient, or you can reserve them, and place several into the batter once you've dropped it down onto the hot griddle.