Preheat oven to 375ºF (190ºC).
In a large mixing bowl combine flour, brown sugar, baking soda and salt. Using a pastry cutter or box grater, cut or grate the cold butter into the flour then gently stir until distributed throughout.
Make a well and pour in buttermilk and egg and stir or mix by hand just until the ingredients begin to come together. Fold in raisins and dried cranberries and keep turning the dough until it starts to look a little sticky and stringy.
Pull dough out onto a floured surface and, using floured hands, fold, turn and shape it into a ball.
Score the top of the loaf with an ‘X’ to allow even heat distribution, then place into baking dish or cast iron skillet and bake for 35-40 minutes until golden and it sounds hollow when you knock on it. Remove from oven, transfer to cooling rack then slice once it’s cool enough to handle.