1. Preheat the oven to 450ºF with a rack in the center. Set a 10- to 12-inch cast-iron or other oven-safe skillet on the rack and put 2 tablespoons of the butter in the skillet to melt. (Do not leave the pan in the oven longer than 10 minutes.)
2. In a small saucepan, melt the remaining 2 tablespoons of butter. Set aside to cool.
3. In a blender or food processor, combine the eggs, milk, ﬂour, vanilla, salt, and cooled melted butter. Pulse for 30 seconds to 1 minute, or until the batter is smooth, being sure no lumps of ﬂour remain. Remove the hot skillet from the oven and pour in the batter. Return the skillet to the oven and bake for 20 to 25 minutes, or until the pancake is fully puffed and browned on top. Do not open the oven during the ﬁrst 15 minutes of cooking or your pancake might deﬂate.
4. Remove the Dutch baby from the oven and serve with butter, whipped cream, fruit, confectioners’ sugar, and maple syrup . . . go big or go home.