1. Whisk together 1 tablespoon hoisin, the vinegar, honey, ginger, and mustard in a small bowl; salt and pepper to taste, for vinaigrette.
2. Preheat oven to 425 degree F and arrange rack in lower third. Halve leeks lengthwise, then cut crosswise into 1/3-inch-thick slices. Wash thoroughly and drain well. Chop 1/4 cup fennel fronds; reserve. Halve fennel bulbs lengthwise, core and halve again lengthwise, then cut crosswise into 1/4-inch-thick slices.
3. Lightly coat a large nonstick shallow baking pan with cooking spray. Toss together leeks, fennel, mushrooms, and allspice in prepared pan. Roast, stirring occasionally, until golden, about 18 minutes. Stir in half of garlic and roast 2 more minutes.
4. Meanwhile, rinse chicken and pat dry. Arrange, in a single layer, over vegetables. Stir together remaining 2 tablespoons hoisin and garlic in a small bowl; spoon evenly over chicken. Roast until chicken is cooked through, about 17 minutes.
5. Transfer chicken to a cutting board and let stand 5 minutes before cutting crosswise into thin slices.
6. Meanwhile, transfer vegetables to a bowl; toss with escarole, fronds, and three-quarters of vinaigrette. Divide between serving bowls and top with chicken. Serve remaining vinaigrette on the side. Makes 4 servings.