In a medium-size heatproof bowl, soak the bulgur in the boiling water for 15 minutes or until the liquid is absorbed. Meanwhile, bring a stockpot of unsalted water to a boil. Place the whole cabbage in the boiling water for about 2 minutes. Remove the cabbage and cut off 4 leaves at the core. Repeat twice more, remove 12 leaves altogether. (Reserve the remaining cabbage for another dish). Return the leaves to the boiling water and cook for 4 minutes or until crisp-tender. Drain, rinse under cold water to stop the cooking, and pat dry with paper toweling.
Heat the oil in a 10" nonstick skillet over moderate heat. Add the onion, red pepper and mushrooms and sauté for 5 minutes. Stir in the zucchini, basil, salt, thyme, mint and black pepper. Partially cover and cook, stirring occasionally, for 10 minutes or until the vegetables are soft and the liquid has evaporated. Stir in the bulgur. In a small bowl, beat the egg white and lemon juice and add to the bulgur-vegetable mixture. Stir in 1 cup of the cheese.
Preheat the oven to 400°. Lightly grease a 13"x9"x2" baking dish. Spoon ¼ cup of the bulgur mixture into the center of a cabbage leaf. Fold the sides of the leaf toward the center, then roll up the leaf and place, seam side down, in the prepared baking dish. Repeat with the remaining leaves and filling.