Preheat the oven to 400 degrees F.

Using a large balloon whisk, whip the eggs and milk together for about 60 seconds.

Add flour, sugar, and vanilla.  Whip for another 60 to 90 seconds to incorporate as much air as possible.  The batter should be completely smooth.  Alternately, blend all ingredients in a blender for about 60 seconds.

Place a well-seasoned cast iron skillet on the stovetop and get it very hot.  Add 3 tablespoons of butter and melt completely.

Pour the batter into the hot cast iron and insert the pan into the oven.

Bake for 20 minutes at 400 degrees F until puffed and brown.

Remove from the oven and serve hot, topped with your choice of butter, lemon juice, sugar, syrup, fresh fruit, yogurt, or jam.