Cut tofu in half horizontally to make 2 pieces, each about 3/4-inch thick. With a 2-inch biscuit cutter, cut 6 rounds from each half to make a total of 12 rounds. In a bowl combine 2/3 cup vegetable broth, 1 1/2 tablespoon hoisin sauce and 1/2 teaspoon sesame oil. Place a non-stick frying pan over medium heat until hot. Add 1 tablespoon cooking oil, swirling to coat sides. Add tofu and cook, turning once, until golden brown, about 1 1/2 minutes on each side. Remove pan from heat. Place a wok over high heat until hot. Add remaining 1 tablespoon oil, swirling to coat sides. Add leek, chili pepper and all mushrooms. Stir-fry for 1 minute. Add sauce. Reduce heat to low, cover and simmer until mushrooms are tender, about 5 minutes. Add cornstarch solution. Cook, stirring, until sauce boils and thickens. To serve, arrange tofu in a circle around the edge of a serving platter. Place mushroom mixture in the center.