Breakfast Strata

Grease a 9x13-inch baking dish. Spread the cubed bread in an even layer in the dish.

In a large skillet over medium-high heat, cook the sausage, breaking it up with a wooden spoon, until browned and cooked through, about 8 minutes. Add the onion and garlic and cook until softened, about 3 minutes. Stir in the spinach and cook until warmed through, 1-2 minutes.

Spread the sausage mixture evenly over the bread cubes. Sprinkle 1 1/2 cups of the cheddar and all of the Gruyere cheese on top.

In a large bowl, whisk together the eggs, milk, mustard powder, salt, and pepper. Pour the egg mixture evenly over the bread and sausage layers. Sprinkle with the remaining 1/2 cup cheddar. Cover tightly with plastic wrap and refrigerate for at least 1 hour or overnight.

When ready to bake, preheat the oven to 350°F. Remove the strata from the fridge and let sit at room temperature while the oven preheats.

Uncover the strata and bake until puffed, golden brown, and set in the center, about 60-70 minutes. If the top starts browning too quickly, loosely cover with foil.

Remove from the oven and let cool for 5-10 minutes before sprinkling with parsley and serving warm.