Udon Noodle Soup with Pork

INGREDIENTS

• 4 quarts water
• 1/2 lb. fresh or 3/4 lb. dried udon noodles
• 1 lb. pork tenderloin, partially frozen
• 2 quarts low-sodium beef or chicken broth
• 1 carrot, peeled and cut into julienne
• 4 fresh shiitake mushrooms, brushed clean, stems removed and caps thinly sliced
• 1 1/2 oz. enoki mushrooms, trimmed and rinsed
• 1 Tbs. peeled and grated fresh ginger
• 1 or 2 fresh red chilies
• 1/4 cup mirin
• 1 Tbs. soy sauce
• 1 tsp. sugar, or to taste
• 1 bunch watercress, stems removed
• 1 bunch green onions, including 2 inches of green tops, thinly sliced
• 1/4 cup sesame seeds, lightly toasted