For the broth, bring all ingredients to a simmer. Reduce to 1 cup and strain. Set aside.

In a large saucepan, heat the sesame oil and olive oil over high heat until smoking. Add the garlic, red pepper flakes, ginger and scallions and stir for 5 seconds. Add the mussels and stir to coat. Cover the saucepan and allow to cook for 2 minutes. Add the lemon grass broth, and cook, still covered, for 2 more minutes, or until heated through and mussels are beginning to open. Add the coconut milk and cilantro and stir to combine well. Divide the mussels among 2 large bowls and ladle the broth over all. Serve immediately.