Heat a large skillet over medium heat and add 1 lb ground pork breakfast sausage. Cook for 8 to 10 minutes, breaking it into small crumbles with a wooden spoon, until brown and cooked through.

Drain the cooked sausage thoroughly in a colander lined with paper towels to remove excess fat, then set aside to cool for 5 minutes.

Grease a 9x13-inch baking dish with nonstick cooking spray or butter.

Spread half of the sourdough bread cubes (4 cups) evenly across the bottom of the prepared baking dish.

Scatter the drained cooked sausage and 1 cup of the shredded sharp cheddar cheese evenly over the bread layer.

Top with the remaining 4 cups of sourdough bread cubes and the remaining 1 cup of shredded sharp cheddar cheese.

Whisk together 8 large eggs, 2 cups whole milk, 1/2 cup heavy cream, 1 tsp Dijon mustard, 1/2 tsp salt, 1/4 tsp ground black pepper, and 1/8 tsp ground nutmeg in a large mixing bowl until fully combined.

Pour the egg mixture evenly over the bread and cheese layers in the baking dish.

Press the top bread cubes down gently with a spatula so all bread pieces are moistened by the egg liquid.

Cover the baking dish tightly with aluminum foil and refrigerate for at least 8 hours, or up to 24 hours.

Remove the baking dish from the refrigerator 20 minutes before baking to take off the chill, and preheat your oven to 350°F (175°C).

Bake covered with foil at 350°F (175°C) for 30 minutes.

Remove the foil and bake uncovered for an additional 20 to 25 minutes, until the center is set (160°F on an instant-read thermometer) and the top is golden brown.

Transfer the dish to a wire rack and let it rest for 10 minutes before slicing and serving.