Heat a 10-inch cast-iron skillet in a preheated oven to 425°F (220°C).
Gather all the ingredients in a bowl and combine them, meaning: add the milk, eggs, salt, melted butter, and the sourdough discard into it – make sure that the butter isn't too hot before storing it.
Whisk everything until it’s perfectly smooth, you can also use a mixer or a food processor to make things easier and faster. The texture should be pancake batter-like but a tad thinner.
Toss some fresh herbs, but keep a few to the side for the final touch.
Remove your 10-inch cast-iron skillet from the oven and add 2 tablespoons of butter. Melt the butter in the skillet over medium heat, then pour the batter over the melted butter and bake until done at 425°F – you're aiming for a bit of a golden puff, which should take about 20 minutes.
Pick your favorite toppings while your Dutch baby gets golden in the oven. Personally, I’m a big fan of runny eggs, so sunny-side-up hits the spot for me. Cut your herbs and prepare also some crumbled cheese if you’re in the mood for it.
Once you’ve gotten that golden puff, dial the oven back to 300°F (150°C) and give it another 5 minutes – this is just to make sure everything's set perfectly.
Take the skillet out of the oven and load it with whatever toppings you love before serving.
Notes
Sourdough Discard – if you don't have any on hand but still want to make this recipe, use an equal amount of yogurt with a little bit of baking powder. Alternatively, you could also try using buttermilk for a similar tangy profile, though you may have to adjust the milk amount.
Whole Milk – Substitute the milk with any non-dairy milk, such as almond, soy, oat, or coconut milk. Though, if you're in the mood for a richer Dutch baby pancake, you can also use cream thinned out with a little water.
Egg – while you can use any commercially available egg replacer, you could also try to use a mixture of water, oil, and baking powder. Though eggs are critical for structure and rise, expect textural differences.