This pretty casserole, layered with colorful vegetables, gets its zip from the exotic taste of sesame tahini and garam masala.
Grease 8-inch square glass baking dish or other 2-quart casserole. Set aside. In food processor or blender, process almonds just until minced. Add yeast and blend briefly by pulsing. Set aside.
In large skillet, heat 2 teaspoons oil over medium heat. Add onion and cook until lightly golden, about 8 minutes. Transfer to medium bowl. In same skillet, heat 2 teaspoons oil. Add leeks and cook 5 minutes, stirring often and lowering heat if necessary. Add to onion, mix well and set aside.
In skillet, heat 2 teaspoons oil. Add carrots and season with salt and freshly ground pepper to taste. Cook, stirring occasionally, 4 minutes. Transfer to another bowl. Heat remaining 2 teaspoons oil in skillet. Add zucchini and marjoram; season with salt and pepper. Cook, stirring occasionally, 2 minutes. Set aside.
Preheat oven to 375F. Make tahini sauce: In small saucepan, heat oil over low heat. Add garlic and cook 1 minute. Stir in tahini and 1 cup water. Simmer 5 minutes. Stir in garam masala, salt and pepper; keep warm until ready to use (do not boil or mixture may curdle).
In prepared baking dish, layer one-third the sweet potato slices, half the leek mixture, another one-third potatoes, then remaining leeks. Top with carrots, zucchini, pepper strips and remaining potatoes; drizzle with tahini sauce. Cover with parchment paper and then foil. Bake until knife inserted in center pierces all layers easily, about 40 minutes.
Remove paper and foil. Sprinkle casserole with reserved almond mixture and bake, uncovered, until lightly golden, about 10 minutes. Serve hot.