Preheat oven to 425 degrees F.
Lay the Mahi fillets onto a greased baking pan. Brush with coconut milk and sprinkle with salt.
In a bowl, mix the melted butter, walnuts, and breadcrumbs.
Bake the fillets in the oven for 10 minutes, then remove and spread the walnut mixture on top of each fillet.
Place back into the oven and back another 10 to 15 minutes, until flakes easily with a fork.