Preheat the oven to 350°F. Peel the potatoes, line a bowl with a clean dish towel, and grate the potatoes on top of the towel. Bring the towel together and wring the liquid out of the potatoes.
Put the shredded potatoes back into a bowl, add the eggs, garlic, Italian seasoning, salt, and pepper, and mix well. Line a springform pan (ø 9 inch) with parchment paper and firmly press the potato mixture on the base and inner wall of the pan. Bake the crust for 25 minutes.
Heat the oil in a pan and fry the onion, bell peppers, ham, and garlic. Finally, add the spinach and cook it down. Then pour the mixture into a bowl.
Add the eggs, milk, Swiss cheese, and pepper to the filling and mix well. Pour the entire mixture into the pan and bake at 325°F for 45 minutes.