Preheat your oven to 400°F and line a baking sheet with parchment paper.
Slice the eggplant into 1/4-inch thick rounds. Pat them dry to remove excess moisture.
In a shallow bowl, add the chickpea flour. Lightly season with salt, pepper, and your favorite Italian herbs.
Dip each eggplant slice into the chickpea flour, ensuring an even coating on both sides.
Place the coated eggplant slices on the prepared baking sheet and drizzle lightly with olive oil.
Bake the eggplant slices for 20-25 minutes, flipping halfway through, until they are crispy and slightly golden.
While the eggplant bakes, warm the tomato sauce in a small saucepan over medium heat. Once warm, remove from the heat.
Prepare your whole wheat bun by slicing it open. Layer the bottom half with the baked eggplant slices.
Top the eggplant with a layer of warmed tomato sauce, followed by the part-skim mozzarella cheese and a generous sprinkle of grated Parmesan.
Place the bun (open side up) in the oven for an additional 3-5 minutes, allowing the cheese to melt and become bubbly.
Meanwhile, in a nonstick pan, cook the egg to your preference (for a baked egg, you can also place it in the oven for a few minutes until set).
Assemble the sandwich by placing the cooked egg on top of the melted cheeses, then cap it with the top half of the bun.
Serve immediately and enjoy your crispy, savory Eggplant Parmesan Sandwich.