How to Make It
Mix the spices, herbs and 1 tablespoon each of salt and pepper with 1 1/2 cups of the oil. In a very large bowl, combine the mushrooms, fennel, red peppers, eggplant, asparagus and whole scallions and gently toss with most of the seasoned oil. Brush the onion slabs with the remaining seasoned oil.
Light a grill and oil the grate. Working in batches, grill the vegetables over moderately high heat, turning, until tender and charred, 10 minutes per batch. Arrange the vegetables on a platter and keep warm.
In a small bowl, whisk the yogurt with the minced scallions, lime juice and remaining 1/4 cup of oil. Serve the vegetables with the yogurt sauce and grilled bread.