1. For the spice broth, heat a large ovenproof nonstick skillet over medium-high heat. Add chile and toast about 1 minute, pressing lightly, until slightly darkened. Transfer to medium saucepan; add chicken broth, beef broth, ginger, cinnamon stick and star anise. Bring to a boil; reduce heat and simmer 30 minutes.
2. Meanwhile, start to bring 3 quarts water to a boil in a large saucepan. Heat oven to 350 degree F.
3. Crush Szechwan peppercorns with rolling pin. Combine with salt in cup and rub on both sides of steaks. Heat oil in same skillet over high heat; add steaks and brown, 1 minute per side. Transfer skillet to oven and bake steaks 9 to 12 minutes, until instant-read thermometer inserted in each steak registers 142 degrees F for medium-rare. Transfer to a cutting board.
4. Add noodles to boiling water and boil 4 minutes, just until tender. Drain in colander and rinse quickly.
5. Line a fine strainer with double-thickness cheesecloth set over a large glass measure. Pour broth through strainer, then return to saucepan. Stir in tamari and garlic. Bring just to a boil.
6. Slice steaks. Divide noodles and watercress among 4 large soup bowls. Divide and add hot broth to each bowl. Top with steak. Makes 4 servings.