DO-AHEAD TIP: Marinate halibut overnight or for at least 4 hours (see recipe).
In a blender or food processor, combine first 6 ingredients (basil through coconut milk); blend until smooth.
Place halibut in a large zipper-topped plastic bag and pour coconut milk mixture over the top; seal the bag and refrigerate overnight or for at least 4 hours.
At time of cooking, remove halibut from the refrigerator.
Melt the coconut oil in a large skillet over medium-high heat; add halibut (reserving marinade) and cook for 4 to 5 minutes per side or until fish flakes easily when tested with a fork.
Remove halibut from skillet and keep warm. Reduce skillet heat to medium and add reserved marinade; whisk for 1 to 2 minutes then reduce heat to low and simmer for 10 minutes or until sauce has reduced.
Serve sauce over fish.