Chocolate Dutch Baby

Preheat oven to 425 degrees F. In a blender, combine milk, eggs, flour, cocoa powder, salt, vanilla, and granulated sugar. Blend until well combined, about 1 minute.

In a large cast-iron skillet, melt butter over medium heat. Pour batter into skillet and immediately transfer to oven. Bake until puffed and set, about 20 minutes. Remove from oven and dust with powdered sugar. Serve immediately with strawberries, if desired.

Note: If you don't have a cast-iron skillet, you can use a round cake pan.