Prepare the streusel topping by combining the Flour butter and brown sugar it should have a nice grainy texture, mix in the pecans and reserve for topping the cake
In medium mixing bowl add the Muffin mix, eggs, milk and chopped fruit. Mix, until fully incorporated.
In a 9” cask iron skillet, heat on medium low for about 5 min with the oil (a deep dark secret here is to use good old bacon grease or half oil and half grease)
Pour the cake mixture into the skillet (note: it is critical that the pan is hot and evenly heated, but not smoking.) Top with the streusel mix and bake at 350 for 25-30 min