Fruity crumble muffins

Every morning our shops are filled with the sweet scent of buttery crumble muffins. Baking these is the first job of the day so that we can have them ready for our first customers on their way to work. Originally, we studded them with seasonal fruit, but our chefs have since come up with so many flavours that we could probably dedicate a whole book to them. The nutty crumble topping gives them a great British twist. To ring the changes, try replacing the fruit according to the variations op