Make the batter: Preheat your oven to 425°F. For this recipe, use a 10-inch cast-iron skillet. Add the skillet to the oven. Let it preheat in the oven, and then add an extra 10 minutes so it is very hot.
Add eggs, milk, flour, salt, brown sugar, and vanilla extract to a food blender.
Blend until smooth. Let the batter rest for 10 minutes.
Prepare the skillet:
Grease the skillet; carefully remove the skillet from the oven and add butter. Swirl the butter around the skillet so the bottom and sides are nicely covered.
Add the batter:
Add the batter; Pour the batter into the skillet while it is still very hot. Immediately add fresh blueberries and bake the Dutch baby for 15 minutes or until puffed.
Serve:
Carefully slice the Dutch baby and serve it warm.
Notes
You can use blueberries or other berries for this recipe. I like to add them because they turn into jam during baking, so you have extra flavor. You can also serve the Dutch baby with fresh berries.