Place the eggplant rounds on a baking sheet. Generously salt the slices and leave them to “sweat” for 20 minutes, then wipe them off with a paper towel.
Preheat oven to 400°F. Brush slices with 2 tablespoons oil and season with black pepper. Bake until softened and slightly golden brown, 30 minutes.
Meanwhile, arrange mushrooms on a sheet pan and toss with remaining 2 tablespoons olive oil. Season with salt and pepper and bake until golden brown, 30 minutes.
Remove eggplant slices from the oven and pour about 2 tablespoons of the sauce mixture onto each one. Sprinkle mozzarella and parmesan on each eggplant slice and top with roasted mushrooms.
Return to oven and bake until cheese is melted, 5 minutes. Garnish with crushed red pepper, fresh basil, and serve immediately.
Notes
Storage: Leftovers will keep well for two days in the fridge and can be reheated in the oven.Tips: don't skip salting the eggplant rounds. If you don't they can become very soggy.