Dinner Tonight: Niku Udon

INGREDIENTS

• 1 quart water, at room temperature
• 1 large pieces of kombu, approximately 10 by 4-inches, or about 1/2 ounce total, rinsed
• 1 1/2 cups packed katsuobushi (dried bonito flakes)
• 1/2 cup plus 2 tablespoons Japanese soy sauce
• 1/2 cup mirin
• 8 ounces beef, very thinly sliced
• 1/2 cup firm tofu, cut into 1/4-inch cubes
• 2 scallions, ends trimmed, chopped into 1-inch pieces
• 1 pound dried udon noodles
• 1/2 cup watercress