Preheat the oven to 425°F (220°C) and line a baking sheet with parchment paper.

Slice the eggplant into even ¾-inch (about 2 cm) thick rounds (two for each burger). Place on the baking sheet and toss with oil, salt, and pepper. Set aside.

In a bowl, gently mix the ground beef with a pinch of salt and pepper. Form into the total number of burgers listed in the recipe details. Add the patties to the baking sheet with the eggplant.

Bake for 12–20 minutes, until the beef is fully cooked with no pink remaining inside, and the eggplant is browned and fork-tender. The eggplant may need slightly longer than the beef, but it should remain firm and not overly soft.

Allow the eggplant to cool slightly. Spread Dijon mustard on the bottom slice of eggplant, then stack the burger with the greens between two slices of eggplant. Add any other low-calorie toppings you like, then serve.