How to Make It
In a medium bowl, combine the ground turkey, bread crumbs, Parmesan cheese, parsley, scallions, 3/4 teaspoon salt, the pepper, milk, and egg. Form the mixture into four patties, each about 1-inch thick.
In a large nonstick frying pan, heat the oil over moderate heat. Add the turkey burgers and cook for 5 minutes. Turn and then top each burger with the provolone cheese. Cook until just done, about 6 minutes longer.
Meanwhile, in a small bowl, combine the mayonnaise and the pesto. Cut the focaccia into quarters. Cut each piece in half horizontally. Spread the cut surfaces of each piece with the pesto mayonnaise.
Top the bottoms of the focaccia with the turkey burgers and then the tomato slices. Sprinkle the tomato with a pinch of salt. Cover with the top piece of focaccia.
Burgers go best with other finger food—oven-roasted potato wedges and raw carrot or fennel sticks, for example.