Pre-heat oven to 375°F.
Squeeze as much water out of the defrosted spinach as possible, then set aside.
Place the shredded potato in a tea towel or a couple of layers of paper towels and squeeze out as much moisture as possible. Place into bowl, add garlic powder, onion powder and 1/2 tsp of sea salt, then toss together.
Heat the ghee or oil of choice in a 10.5-inch skillet over medium heat. Add the potato to the skillet, spread it out into an even layer and press down over the entire surface with a spatula. Let cook, without disturbing, until bottom is golden brown. Flip and let cook an additional 2-3 minutes.
Meanwhile, whisk together the eggs and milk. Add the spinach and cheese and remaining 1/4 tsp of sea salt and gently whisk until combined.
Once the flipped hash browns have cooked for 2-3 minutes, pour the egg mixture into the skillet. Let cook until the edges of the eggs have begun to set. Place into heated oven and cook until the center is just set, about 15-20 minutes.
Let cool for about 5 minutes, then cut and serve.