Step 1

Adjust oven racks to lower and middle positions. Heat oven to 450 degrees F. Lightly oil a large rimmed baking sheet. Beat the egg and egg white in a shallow bowl and place the flour in a separate shallow bowl. In a third bowl, combine the panko with the Parmesan, 1 tablespoon oil, and 1/2 teaspoon each salt and pepper.

Step 2

Slice the eggplant into 1/2-inch-thick rounds. Dip the rounds in the flour, then the eggs (letting any excess drip off), and finally in the bread crumb mixture, pressing gently to help it adhere; transfer to the prepared baking sheet. Roast on the lower oven rack until the eggplant is golden brown, 20 to 25 minutes.

Step 3

On a second rimmed baking sheet, toss the tomatoes with 1 tablespoon oil and 1/4 teaspoon each salt and pepper; transfer to the oven and roast on the middle rack for 10 minutes. Remove from the oven, scatter the spinach over the top and toss until beginning to wilt.

Step 4

While the vegetables are in the oven, in a medium bowl, whisk together the vinegar and remaining tablespoon oil with 1/4 teaspoon each salt and pepper. Add the onion, mozzarella, and basil and toss to combine. Serve the eggplant with the tomatoes and spinach and spoon the vinaigrette over the top.