Preheat oven to 220 C. Place the skillet in the oven to heat for at least 8 minutes.
Whisk all the ingredients except the butter in a blender until smooth.
Melt the butter in a skillet and oil the sides of the skillet. Pour all of the dough into the center of the pan.
Return the skillet and dough immediately to the oven and bake for 16-18 minutes, until the pancake is light and lightly browned around the edges.