Preheat your oven to 425°F and line a baking sheet with parchment paper.
Slice the eggplant into approximately 1/2-inch thick rounds. Lightly salt them and let sit for 10 minutes to draw out extra moisture, then pat dry.
In a shallow bowl, whisk together the whole egg and egg white. In another plate, combine the whole wheat breadcrumbs with the grated Parmesan cheese. (Optional: add a pinch of garlic powder, salt, and pepper to the breadcrumb mixture for extra flavor.)
Dip each eggplant slice first in the egg mixture, then dredge in the breadcrumb mixture until well coated. Place the coated slices on the prepared baking sheet and lightly spray with olive oil.
Bake the eggplant slices for about 20 minutes, flipping halfway through, until they become crispy and golden.
While the eggplant bakes, toast the whole wheat roll either in a toaster oven or on a skillet until lightly crispy.
Remove the eggplant slices from the oven and top each with a layer of marinara sauce and a slice of part-skim mozzarella cheese. Return to the oven for an additional 3-5 minutes or until the cheese is just melted.
Assemble your sandwich by placing the baked eggplant slices onto the bottom half of the toasted roll. Top with any remaining marinara sauce if desired, then cover with the top half of the roll. Garnish with fresh basil or a sprinkle of extra Parmesan if you like.
Serve warm and enjoy your deliciously crispy baked eggplant Parmesan sandwich!