Preheat your Panini press according to the manufacturer's instructions, around 375°F (190°C). Spray the plates generously with kitchen pan spray to ensure the hash browns don't stick.

In a medium skillet over medium heat, melt 2 tablespoons of butter. Add the crumbled sweet Italian sausage and cook, stirring occasionally, until browned and cooked through, about 5-7 minutes.

In the same skillet, sprinkle in 3 tablespoons of all-purpose flour, along with 1 teaspoon of dry mustard, a dash of nutmeg, kosher salt, and white pepper to taste. Cook this mixture for 1-2 minutes until golden and fragrant. Gradually whisk in 2 cups of whole milk, stirring continuously until the gravy thickens, about 3-5 minutes.

Using about 4 cups of shredded hash browns, tightly pack them into discs, about ½ inch thick. Grease the Panini press with an additional pat of butter and place the hash brown discs on the plates. Close the press and cook for 5-7 minutes or until golden brown and crispy.

Crack 4 large eggs into a bowl and whisk them together with a splash of milk. Heat a non-stick skillet over medium heat with a touch of butter. Scramble the egg mixture in the skillet for about 3-4 minutes until just set but still soft and fluffy.

Assemble the stacks starting with a crispy hash brown disc as the base, add fluffy scrambled eggs, spoon over sausage gravy, and sprinkle with shredded cheddar cheese. Repeat layers as desired.

Garnish each stack with a sprinkle of chopped chives and serve immediately while hot.