Sift flour, bicarbonate of soda, spices, and salt into a bowl then stir in sugar, suet, dried fruits, and apple.
Mix black treacle, egg, and buttermilk then stir into the dry ingredients to form a soft cake-like consistency.
Dip muslin in boiling water, squeeze dry, and sprinkle a 30cm circle with flour and sugar in the center.
Spoon mixture onto the cloth, tie securely with string, and leave a little room for expansion.
Place the pudding on a trivet inside a large pan and add enough water to almost cover the surface.
Cover with a tight lid and simmer gently for 3 to 4 hours while topping up water as needed.
Preheat oven to 180°C.
Lift the pudding from the pan and dip briefly in cold water before removing the cloth.
Place the pudding on an ovenproof dish and dry in the oven for 15 minutes.
Serve in wedges with clotted cream.