Adjust oven racks to upper middle and lower middle positions and heat oven to 400 degrees. Slice bread in half lengthwise, then slice each half crosswise into 1/2-inch thick pieces. Spread bread in single layers on two baking sheets (it might fit on one sheet) and bake until golden, 15 to 20 minutes, flipping bread and switching and rotating sheets halfway through. Let cool 15 minutes.
Grease 13 by 9 inch baking dish. Lay half of bread in prepared pan so that the edges overlap slightly. Top with half of sausage mixture and 1 cup cheese. Repeat with remaining bread, remaining sausage mixture and the remaining cheese. (If you don't have enough bread for two full layers, that's fine, just space the second layer as evenly as you can, or just make a single layer)
Wrap casserole with plastic and place weights on top (See notes), this weight will help the toasted bread fully absorb the egg-milk mixture. Refrigerate for at least 1 hour and up to 24 hours.
Cover your casserole tightly with plastic wrap and then place another baking dish right on top of your casserole. Fill the empty baking dish with a few large cans of canned food. This will help the all the bread pieces soak up the egg mixture. NOTE: My 9x13 pans are all slightly different in size/shape/depth so some of them don't fit inside of each other. You want the pan filled with cans to be resting right on top of the casserole, so just make sure you use a dish/pan that will fit inside and rest right on top of the casserole.