To clean clams, soak in cold water for 20 minutes with a big pinch of salt. Lift each clam out of the bowl, and individually rinse with water.
Melt ghee in a dutch oven or heavy pot over medium heat, then add shallots, garlic and ginger and sauté for 6-7 minutes.
Add the spices and stir, then add the coconut milk and bring to a gentle boil. Add clams, cover and cook, stirring occasionally, until clams are opened, 6 to 8 minutes (discard any unopened clams).
Serve clams in bowls with cooking liquid and squeeze lime wedge overtop. Sprinkle with cilantro and serve.