In a large skillet, cook bacon over medium-low heat until crisp; drain on paper towels. (If using sausage, cook over medium heat until brown; drain fat.)
Meanwhile, butter bread slices on one side. Cut into 1-inch cubes. Place half the bread cubes in a greased 2-quart square baking dish. Top with half the bacon. Top with remaining bread cubes and remaining bacon; sprinkle with cheese (dish will be full).
In a medium bowl, whisk together eggs, whipping cream, dry mustard, salt and black pepper. Pour evenly over layers in dish. Cover and chill in the refrigerator for 2 to 24 hours.
Bake, uncovered, in a 325 degree F oven for 50 to 55 minutes or until center is set (170 degrees F). Let stand for 10 minutes before serving.