1. Heat the broiler or grill. In a medium bowl, combine the cooking oil, coriander, soy sauce, garlic, 1/2 teaspoon salt, and the pepper. Mix well. Add the mushrooms; coat thoroughly.
2. In a medium saucepan, bring the water to a boil. Stir in the couscous. Cover, remove from the heat, and let stand 5 minutes. Fluff with a fork and transfer to a bowl.
3. Add the scallions, cucumber, tomatoes, cilantro, lemon zest, lemon juice, olive oil, and the remaining 2 teaspoons of salt to the couscous. Toss to combine.
4. Divide the mushrooms among four skewers. Broil or grill the mushrooms, turning occasionally, until they are tender and golden brown, about 10 minutes. Serve over the couscous.
Wine Recommendation: We don't often think of sparkling wine as an accompaniment to food; its usual place is as an aperitif. Here, however, a rosé Champagne, with its crisp acidity, hint of red fruit, and subtle earthy undertow, will be truly exciting.