Brown sausage in a skillet over medium heat, stirring until crumbled and fully cooked.

Drain excess grease from the cooked sausage.

In a large bowl, whisk the eggs lightly.

Add the cooked sausage, cubed bread, salt, dry mustard, and shredded cheddar cheese to the bowl with the eggs.

Mix all ingredients together thoroughly until well combined.

Grease a 9x13 inch casserole dish.

Pour the egg and sausage mixture into the prepared casserole dish.

Cover the dish tightly with plastic wrap or foil.

Refrigerate for at least 8 hours, or preferably overnight, to allow the flavors to meld and the bread to absorb the egg mixture.

Preheat your oven to 350 degrees Fahrenheit (175 degrees Celsius).

Remove the casserole dish from the refrigerator and remove the cover.

Bake in the preheated oven for 45 minutes, or until the center is set and a knife inserted into the center comes out clean.

Let the casserole cool slightly before cutting into squares and serving.