Grease a 9x13-inch baking dish. Spread the cubed bread evenly in the bottom of the dish.

In a large skillet over medium-high heat, cook the sausage until browned. Add the chopped onion and cook for 5-7 minutes, until softened. Stir in the minced garlic and cook for one more minute until fragrant. Drain excess grease.

Sprinkle the sausage mixture evenly over the bread cubes in the baking dish. Top with the shredded cheddar cheese.

In a large bowl, whisk together the eggs, milk, heavy cream, salt, pepper, dry mustard powder, and nutmeg until well combined.

Pour the egg custard evenly over the ingredients in the baking dish. Gently press down on the bread with a spatula to ensure it is saturated. Cover tightly and refrigerate for at least 8 hours or overnight.

The next morning, remove the strata from the refrigerator and let it sit at room temperature for 30 minutes. Preheat oven to 350°F (175°C).

Bake uncovered for 55-65 minutes, until the strata is puffed, golden brown, and a knife inserted into the center comes out clean.

Let rest for 10 minutes before slicing and serving warm.