Soak mussels in a bowl of cold salted water for 20 minutes. Drain.
Bring a small pot of water to a boil. Add noodles; simmer until tender, 2 to 3 minutes. Drain and rinse with cold water.
Bring 1 quart of water to a boil in the same pot. Add tomato, onion, tomato puree, sauerkraut, chile oil, garlic, and salt. Simmer until onion softens, about 10 minutes. Stir in mussels; simmer for 1 minute. Stir in prawns; simmer until opaque, 1 to 2 minutes. Stir in rice noodles. Garnish with parsley.
