Preheat oven to 425°F.

Place a 9×12 baking dish in the oven with the 4 tablespoons of butter. Let the butter melt and the pan get hot while you prepare the batter.

In a blender (or whisk bowl), combine:

• Eggs

• Milk

• Flour

• Vanilla

• Salt

Blend or whisk until completely smooth.

If using sourdough:
Add 100–200g starter and blend again.
Add a small splash of milk and a little extra flour if the batter feels too thick.
(Note: It won’t rise quite as dramatically with sourdough — that’s normal.)

Carefully remove the hot pan from the oven and immediately pour the batter over the melted butter.

Bake for 15–17 minutes. Do not open the oven while baking.

Remove and serve immediately — it will deflate slightly as it cools.