Wash the pepper, split it in half, remove the white core and all seeds, and cut the pepper’s flesh into the finest possible dice.
Trim the root away from the scallions and remove any blemished outer leaves. Cut about 1inch off the tops, wash the scallions in cold water, and slice them into thin rounds.
Put into a small skillet 1tablespoon of butter, the diced pepper, and the scallion rounds, and turn on the heat to medium. Cook for a few minutes, stirring occasionally, until the vegetables are tender and have become lightly browned.
Put the meat, egg, and grated Parmesan in a mixing bowl.
Put the milk in a small saucepan and warm it over gentle heat. Don’t let the milk come to a boil. As soon as you see the first little pearly bubble forming at the edge, take the pan off heat. Add the broken-up soft crumb, mashing it down until it is thoroughly soaked in milk.
Add the milk-soaked crumb to the meat, along with the cooked pepper and scallions, salt, and a few grindings of black pepper. Work the mixture with your fingertips until all ingredients are evenly combined. Shape the resulting veal mixture into six hamburger-shaped patties about 1inch high.
Dredge each patty on both sides in the bread crumbs spread on a plate.
Choose a skillet broad enough to accommodate all the patties on one layer without overlapping. Put in the remaining 2tablespoons of butter and the vegetable oil, and turn on the heat to medium high.
When the fat is hot enough so that a little piece of meat dropped into it will sizzle, slip in all the patties. Brown them quickly on one side and as soon as that is done, turn them over with a flat metal spatula and do the other side.
Add the chopped tomatoes with their juice, turn the patties over once or twice, lower the heat, and cook the tomatoes at a steady but gentle simmer for about 15 or 20 minutes, until they thicken into sauce and the fat begins to separate from the sauce, as described in the Note. Bits of the pepper and scallion may come loose, but this is no cause for concern because they become part of the sauce. Serve piping hot.