Cook bacon until crisp. Remove bacon. Retain 3 Tablespoons of bacon grease OR add cooking oil in 10- or 12-inch oven-proof skillet (cast-iron works great) on medium heat.
Add potatoes. Sprinkle with 1/4 teaspoon salt and pepper. Cook 10 minutes or until almost brown. Turn occasionally with spatula.
Blend eggs with milk, bacon, Italian seasoning and remaining 1/2 teaspoon salt while potatoes are cooking. Stir the eggs into the potatoes.
Bake covered at 350 degrees F for 15 minutes.
Remove from oven. Sprinkle with cheese and return to the oven.
Bake 15 minutes more or until cheese is melted and eggs are set. Allow to cool 10 minutes before cutting into 4 squares. Serve with heated salsa.
Adding cold eggs directly to a hot skillet containing frozen potatoes drops the pan temperature drastically and causes uneven setting. Cast iron retains heat efficiently, making it the ideal vessel for this dish. Preheat the skillet properly over medium heat to ensure the frozen potatoes brown instead of steaming in their own excess moisture. Turn the potato shreds occasionally with a flat spatula until they develop color along the edges, which takes about 10 minutes. Retaining the rendered bacon grease adds robust flavor without requiring extra spending on specialty fats, but measure carefully to maintain the correct ratio. Whisking the eggs thoroughly with milk incorporates air for a lighter texture before pouring the mixture over the potatoes. Cover the skillet securely during the initial 15 minutes of baking at 350 degrees Fahrenheit to trap steam and help the center coagulate evenly. Overcooking causes the eggs to become rubbery and releases unwanted liquid. Add the shredded cheese only during the final 15 minutes of baking so the dairy melts without burning or separating its oils. Allowing the finished frittata to rest for 10 minutes off the heat firms up the structure for clean slicing into portions. Substitute Monterey Jack or Swiss cheese based on what is already available in the refrigerator to minimize grocery expenses. Serve warm alongside heated chunky salsa for contrasting acidity.