Preheat broiler.
In a large bowl, mix beef, onion, garlic, egg, 4 tablespoons of coconut milk, cumin, coriander, cayenne, and salt.
Form into golf-ball size meatballs and place on a nonstick broiling pan.
Broil until meat is browned and no longer pink inside.
Remove meatballs onto a serving dish and discard fat.
Pour remaining coconut milk into the pan, making sure to dissolve all browned residues.
Add cilantro, stirring until blended; pour over meatballs or serve in a bowl on the side.
Serve immediately.