Have a glass, ceramic, or enameled steel baking pan ready. Rub the inside of the pan with the garlic. Lightly oil the pan and set aside.
Adjust the oven rack to the lower third of the oven. Preheat the oven to 375 degrees F.
Layer the vegetables slices into the pan, alternating zucchini, tomato, potato and onion, or arrange the vegetables, starting with the potatoes and ending with the tomatoes.
Sprinkle each layer with salt, pepper and thyme. Drizzle the casserole with a generous amount of olive oil.
Tear up the white bread and pulse in a food processor to make soft crumbs. Remove the crumbs to a bowl and mix with the mustard, parsley, Parmesan cheese, a pinch of salt and freshly ground pepper until well combined.
Top the tian with the crumb mixture and drizzle with about a tablespoon of Stonewall Kitchen Roasted Garlic Oil.
Bake the tian for about 1 hour, or until the vegetables are soft and the crumbs are browned. Allow the casserole to cool for about 20 minutes before serving.