Preheat the oven to 400 degrees . In a large nonstick skillet, heat the EVOO, 2 turns of the pan, and the garlic over medium heat for a minute or so, then discard the garlic. Add the potatoes in a thin layer and season with lots of salt and pepper. Cook until crispy-brown, 8 to 10 minutes. Flip and cook until the other side is crisp, 6 to 7 minutes.
In another large nonstick skillet, melt the butter over medium heat. In a bowl, beat the eggs, milk and hot sauce. Add the mushrooms to the skillet and cook until just softened, about 5 minutes. Add the bell pepper and ham and cook for 4 minutes. Add the scallions and heat through, then add the beaten eggs; season with salt and pepper. Cook until the bottom of the eggs set, then transfer to the oven and cook through, 10 to 12 minutes.
Pile the potatoes on 4 slices of toast and top each with one quarter of the omelet. Cover with the remaining toasts, then cut the sammies corner to corner.