Place a heavy cast iron skillet in the oven and preheat oven to 400°F (200°F).
In a blender, beat the milk, eggs, and vanilla until combined. Slowly add the flour, granulated sugar, nutmeg, and salt and continue to beat until light and smooth.
After 5 minutes, carefully remove skillet from the oven. Add butter to the skillet and immediately return to the oven. As soon as butter is melted, remove the skillet and swirl the melted butter to coat the bottom and sides. Immediately pour the batter into the hot skillet and return skillet to oven to bake until golden brown, about 20 minutes.
When Dutch Baby is done, move it to a serving plate (or leave in skillet) and fill center with berries. Sprinkle with powdered sugar, cut into wedges, and serve. Sausages or whipped cream on the side make great accompaniments.