Preheat oven to 400°F. In a medium bowl, whisk eggs until well beaten and slightly frothy. Whisk in milk, chives and black pepper and set aside. In a large ovenproof skillet, heat olive oil over medium heat until hot but not smoking. Add egg mixture to skillet, and then quickly arrange remaining ingredients, in order, on top of eggs, distributing evenly and attractively. Cook for 3 minutes on the stovetop without stirring, then transfer to oven. Bake until the top is golden brown and the frittata is set, about 30 minutes. (Baking time will vary with the size of the skillet, so continue to bake until center is just firm to the touch). Let cool slightly before serving. Cut into wedges.