Soak the bread in milk for a few minutes.
Sauté the onions in a little butter until soft.
Mix everything together and form into a loaf.
Bake at 180°C / 350°F for about 60–70 minutes.
For the gravy, use the drippings from the pan, add beef broth and mustard, then thicken with the flour slurry.
Serve with mashed potatoes and gravy.
