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Preheat the oven to 350°. In a large bowl, beat the eggs. Beat in the milk, cheese, parsley, basil, salt and pepper.
In an 8-inch ovenproof skillet, heat the oil. Add the shallots and cook over moderate heat until softened, about 7 minutes. Add the tomato and prosciutto and cook, stirring, until warm, about 2 minutes. Pour in the beaten eggs and cook until beginning to set on the bottom, about 3 minutes. Poke the mozzarella cubes in the eggs. Bake until just firm when lightly pressed, about 20 minutes.
Set the skillet over high heat and shake the frittata until it releases from the skillet, about 10 seconds. Place a large, flat plate over the skillet and invert the frittata onto it. Let cool for 5 minutes, then cut into wedges and serve.