Asian Steamed Vegetable Pot with Silken Tofu

Name: Asian Steamed Vegetable Pot with Silken Tofu
Ingredients: 3 tablespoons light soy sauce; 3 tablespoons sake or Chinese rice wine; 1 teaspoon peeled and grated fresh ginger; ½ teaspoon sugar; 3 tablespoons water; 1 medium-size leek (white and light green parts only), cut into 3-inch long slivers, well washed, and drained; 6 cups mustard greens, preferably Chinese mustard greens, coarsely chopped, well washed, and drained; 6 ounces daikon radish, peeled and cut into ¼- to ½-inch-thick rounds; 8 ounces firm silken tofu, cut into 1-inch cubes, for topping; 3 ounces enoki (straw) mushrooms, stems trimmed, for topping