Step 1: Preheat your oven to 425°F (190°C). Lightly grease a 9x13-inch baking dish. In a medium mixing bowl, combine the thawed hash browns, melted butter, salt, and pepper. Mix well.
Step 2: Press the hash brown mixture evenly into the bottom of the prepared baking dish to form a crust. Bake for 25 to 30 minutes, or until the edges are golden and slightly crisp. Remove from the oven and set aside.
Step 3: Lower the oven temperature to 375°. In a large mixing bowl, whisk together the eggs, milk, and heavy cream.
Step 4: Add the softened cream cheese, onion powder, salt, and black pepper. Whisk together, there will be small lumps of cream cheese. Fold in the scallions, crumbled bacon, diced jalapeños, and 1 cup of shredded cheddar cheese.
Step 5: Pour the egg mixture over the baked hash brown crust. Sprinkle the remaining cheese on top.
Step 6: Bake for 30-35 minutes or until the center is set and the top of the casserole is golden bubbly. Baking time will vary by oven. Check the internal temperature in the center of the casserole with a meat thermometer to confirm it's reached 160°. Let the casserole rest for 5-10 minutes before slicing and serving.