To make the dumplings: Roughly break the bread into a large bowl. Bring the milk to a boil and pour over the bread. Cover and let it soak for 2 hours.
Heat some olive oil in a pan and cook the onions until soft and lightly browned. Add the garlic and after a couple of minutes, the mushrooms. Cook until the moisture that escapes from the mushrooms evaporates, about 5 minutes. Season with salt and pepper.
Add the onion and mushroom mixture and the chopped parsley to the bread. Mix well to form a dough – the dough should be soft and moist but firm enough to form balls. If it’s too dry, add more milk. If it’s too wet, add some breadcrumbs, plain flour or semolina.
Wet your hands and roll the dough into balls, slightly bigger than a golf ball.
Put a pot of salted water to boil. Once the water comes to a rolling boil, reduce the heat so it simmers. Add the balls into the water with a slotted spoon and cook for 15-20 minutes or until they bob to the surface. Remove and drain.
Optional: Once drained, heat some butter in a skillet and gently toast the dumplings in the butter for a couple of minutes until lightly browned.
For the sauce: Heat the butter in a saucepan. Add the minced onions and cook till soft and translucent. Add the mushrooms and cook till slightly browned (make sure the mushrooms all touch the hot surface of the pan and are not piled in a heap as this will make them soggy and prevent them from browning nicely). Reduce the heat and add the cream and milk. Stir. Add the cider and then season. Remove when the sauce reaches the consistency you desire.