Preheat oven 190 C. Grease an oven-safe skillet with butter and set aside. 

In a shallow saucepan, melt butter over low heat. In a medium-sized bowl, combine flour, sugar, milk and melted butter. Whisk just until combined. Gently fold in the blueberries into the batter. Pour mixture into the greased skillet.

Bake for 40 minutes or until light brown on the edges. Remove from oven and let cool before slicing. This is best served hot or cold with a dollop of sour cream.