In a small stock pot on high heat, coat lightly with olive oil and saute the leeks, sliced garlic, kaffir, lemongrass, and ginger until soft, about 3 minutes. Add the mussels and clams, stir, and season. Deglaze with wine, and cover, to steam open the shellfish.
Check after 3 to 5 minutes, most of the shellfish should be slightly opened. Remove and discard the tightly closed shellfish. Add the stock. Bring to a simmer and reduce by 1/3.
Meanwhile, in a small saucepan coated very lightly with olive oil, saute the smashed garlic until light brown. Add the saffron and stir. Season and add the cream. Bring to a simmer and reduce by 1/3. Transfer to a blender and puree smooth. Check for seasoning.
Remove and discard the kaffir, lemongrass, and ginger pieces. Add the fish sauce and check for seasoning.
While still simmering, add the cod and shrimp, and cook for 3 minutes. Then add the crab and lime juice and check again for flavor.
In 4 heated rice bowls, ladle the soup with the seafood. Serve immediately, drizzled with Saffron-Garlic Foam, or, if possible, place the warm Saffron-Garlic Foam in a cream canister with 2 cartridges and foam on top of the soup.