Preheat oven to 400°F (200°C). Grease four 4-inch ramekins or individual baking dishes. In a large bowl, combine thawed hash browns, melted butter, garlic powder, onion powder, smoked paprika, salt, and pepper. Mix until evenly coated. Press 1/4 of the mixture into the bottom of each ramekin, creating an even layer about 1/2-inch thick.

Place ramekins on a baking sheet and bake for 15 minutes until golden brown and crispy around the edges. Remove from oven and reduce temperature to 375°F (190°C).

While hash browns bake, whisk together eggs, heavy cream, Dijon mustard, 3/4 cup Gruyère, 1/4 cup Parmesan, and a pinch of salt and pepper until well combined but not frothy.

Divide half of the egg mixture evenly among the four ramekins, pouring over the baked hash brown layer. Sprinkle with remaining 1/4 cup Gruyère. Add another layer of remaining hash brown mixture, pressing gently. Top with remaining egg mixture and sprinkle with remaining 1/4 cup Parmesan.

Return ramekins to oven and bake at 375°F (190°C) for 25-30 minutes, until eggs are set but still slightly jiggly in the center, and tops are golden brown.

Remove from oven and let rest for 5 minutes. Run a knife around the edges, then carefully invert onto serving plates. Garnish with fresh herbs, flaky sea salt, and freshly ground black pepper.