Combine the half-and-half, eggs, Worcestershire, Tabasco, and salt in a bowl and blend well.
Slice the bread into thin (about 1/4 inch) slices. Butter the inside of a 9"x5"x4" baking dish or casserole. Place a layer of bread along the bottom. Sprinkle one-third each of the cheese, mushrooms, and green onions over the bread. Pour one-fourth of the milk-egg mixture over this, enough to soak it well. Push down gently until the bread is soaked.
Repeat the layers in the same order as above, following with a dousing of liquid. Finish with a layer of bread and the last of the liquid.
Place the baking dish in a pan of warm water and put the entire assembly into the preheated oven. Bake for an hour and 15 minutes at 300 degrees. Let it cool for at least a half-hour before serving. It can be sliced, but it’s perfectly fine to spoon it right out of the dish at the table.
