In a large skillet, heat a bit of oil over medium heat. Add 2 cups of chopped spinach and sauté until wilted, about 2-3 minutes. Remove the spinach from the pan.

In the same pan, add 2 cups of frozen shredded hash browns and cook until golden brown, stirring frequently. Season with salt and pepper to taste.

Grease a bundt pan generously with butter or non-stick spray. Layer half of the diced bread cubes (about 4 cups) into the bottom of the pan. Evenly distribute the diced ham, sautéed spinach, and 1/4 cup chopped green onions over the bread. Spread the hash browns on top, followed by half of the shredded cheese (1 cup). Finish with the remaining bread cubes.

In a large mixing bowl, beat together 12 large eggs, 2 cups of milk, 1 cup of heavy cream, 1/2 teaspoon salt, 1/2 teaspoon black pepper, 1 teaspoon dry mustard, and a large pinch of cayenne pepper. Pour this mixture evenly over the layers in the bundt pan, pressing lightly to help the custard soak into the bread. Let sit for at least 30 minutes, or cover and refrigerate overnight.

Preheat your oven to 400°F (200°C). Sprinkle the remaining 1 cup of shredded cheese over the top. Place the bundt pan in the oven and bake for 40-45 minutes, or until the top is golden brown and a knife inserted into the center comes out clean.

Once baked, let the bundt cool for about 10 minutes. Place a large, flat plate over the top of the pan and carefully flip it over to release the breakfast bundt. Slice into portions and serve warm, garnished with fresh parsley if desired.