Fry the bacon in a large non-stick pan in the oil until cooked and then set aside using a slotted spoon.
Sweat the onions on a low heat in the same pan with a lid for about 5 minutes.
Stir in the chopped mushrooms and sweat for a further 5 minutes under a lid.
Sieve the flour, mix in the salt and suet and then add the water to give a firm dough which comes away from the sides of the bowl cleanly.
Roll out the dough to a rectangle shape the same width as the pudding sleeve about 1/4 “ thick.
Lay the bacon and onions/mushrooms over the dough leaving a gap along the sides and the bottom edge.
Season with the pepper and a little mace if using.
Roll up the pudding and seal the sides and bottom edge with a dab of water.
Put in pudding sleeve or roll up in a layer of grease proof paper and foil loosely (to allow for expansion) and scrunch foil to seal.
Place in a steamer over boiling water for 2 hours topping up the water regularly.
Once ready slice up and serve with your favourite vegetables and gravy or tomato ketchup if preferred.