Slice the tomatoes into rounds 1/4-inch thick. Cut the potatoes, leaving the skin on, into equally sized rounds. Peel the onion, leaving whole, cut into thin round slices.
Cut the pepper in half, remove and discard the seeds and ribs, and cut into a thin julienne.
Leave the skin on the eggplant and cut into thin round slices.
Trim the top of the fennel bulb and slice the fennel on a vegetable slicer into thin slices beginning at the base and continuing up to the top.
Using a large ceramic vegetable gratin dish, brush the bottom of the dish with some of the olive oil. Lay the sliced tomatoes on the bottom of the dish in single layer overlapping where necessary. Season this and each succeeding layer of vegetables with salt and pepper as you go to ensure balanced flavors.
Lay the potatoes on top of the tomatoes, season and continue with a layer of onion.
Combine the peppers and lay the peppers over the onion layer. Next add a layer of eggplant and finally a layer of thinly sliced fennel remembering to carefully season each vegetable layer.
Drizzle 3 tablespoons of olive oil over the top layer of vegetables and place the dish into the oven. Bake for 45 minutes.
While the gratin is baking, combine the remaining olive oil with the garlic, mint, bread crumbs, cheese and season with a fresh grind of black pepper. After the vegetables have cooked for 45 minutes, remove from the oven, sprinkle the bread crumb mixture over the top and return to the oven for another 15 minutes or until the top browns to a golden color.