Place top oven rack in the center position and pre-heat oven to 425°F.
To prepare the potato crust, combine the shredded potatoes, butter, Italian seasoning, and garlic powder in a large bowl. Generously season with salt and black pepper, to taste, and toss to combine. Set aside.
Add olive oil to a 10½” well-seasoned cast iron or other non-stick oven-safe skillet set over medium heat. Add the pancetta, bell pepper, red onion, Italian seasoning, and garlic powder. Season with salt and black pepper, to taste, and stir to combine.
Cook, stirring frequently, until the pancetta is browned, and the vegetables are crisp-tender, approximately 4-5 minutes. Transfer contents of skillet to a bowl and set aside.
Allow the skillet to cool for several minutes before adding the potato mixture. Carefully form a crust with your fingers by pressing the potatoes into a uniform layer along the bottom and up the sides of the skillet.
Place the skillet in the pre-heated oven and bake for 15-20 minutes, or just until the potato crust is lightly browned. Remove from oven and reduce oven temperature to 350°F.
While the crust is baking, add the eggs, milk, and three-quarters cup of the cheese blend to the sautéed vegetable and pancetta mixture. Whisk to thoroughly combine and set aside.
Pour the egg mixture into the baked potato crust shell and top with remaining cheese. Place in the 350°F oven and bake for 25-30 minutes, or until a knife inserted in the center comes out clean. Remove from oven and cool for 15 minutes. Sprinkle top of frittata with fresh chopped parsley before serving.