In a saucepan over medium heat, add all but 1/4 cup of the coconut milk, coconut cream, and mint. Stir frequently to prevent scorching. Once the cream bubbles around the edges, turn the heat off, and let the mint steep for 1-2 hours.
After steeping, strain the mint out of the mixture, and add in the sugar, salt, and vanilla. Add the arrowroot starch to the reserved coconut milk, and mix until there are no lumps. Add to the pot.
Bring the saucepan up to a gentle boil, stirring consistently, until the mixture thickens, about 5-7 minutes.
Transfer to a shallow casserole pan, and allow to cool for 10 minutes. Then, place a sheet of plastic wrap in direct contact with the surface of the ice cream base. This will prevent it from developing a skin. Place in the refrigerate, and allow to completely chill, 3-4 hours.
Remove the base from the refrigerator, and add to your ice cream machine. Turn the machine on, and churn for 15 minutes.
While the ice cream begins to churn, add the chocolate chips and oil to a microwave-safe bowl, and microwave on high for 30 seconds. Remove from microwave, and mix. If chunks of chocolate still remain, microwave for an additional 15 seconds.
When the ice cream has churned for 15 minutes, it's time to add the melted chocolate. Adding the chocolate in it's melted form while the ice cream continues to churn, makes for perfect shards of chocolate in your ice cream. In 4 batches, slowly pour in the melted chocolate, allowing time after each addition, for it to make it's way all around.
Once all the chocolate has been evenly distributed, move to a freezer-safe container with a lid, and freeze for 3-4 hours.
To serve, top with toasted coconut, a sprig of mint, and chopped walnuts.