Set a medium sized bowl over a large container of ice water. Place the coconut in a large, heavy saucepan and set over medium-high heat. Stir the coconut until it begins to brown, about 7 minutes. Add the coconut milk, cream, vanilla extract and 1/4 cup sugar, stirring occasionally, until steam appears and the liquid is hot (175 degrees). Remove from heat. Cover and let stand for 30 minutes. Pour the coconut mixture through a medium-mesh strainer set over a bowl, pressing on the coconut to extract as much liquid as possible; discard the coconut. Return the liquid mixture to the same saucepan and set over medium-high heat. Stirring occasionally, cook until steam appears and the liquid is hot (175 degrees). Meanwhile, in a separate bowl, whisk the yolks and 1/4 cup of sugar together until smooth. Slowly whisk about 1 cup of the hot liquid mixture into the yolks to temper them. Then slowly whisk the tempered yolk mixture back into the remaining hot liquid mixture. Continue to cook the custard mixture over medium heat until it is very hot but not simmering (180-185 degrees). Immediately pour custard into bowl set in the ice bath and let cool, stirring occasionally, for about 10 minutes. Remove the custard mixture from the ice bath. Cover tightly with plastic wrap and refrigerate until very cold (40 degrees), at least 4 hours and up to 24 hours. A few minutes before you plan to churn the ice cream, place semisweet chocolate in a medium heatproof bowl. Set bowl over saucepan containing barely simmering water; heat mixture until chocolate is melted and whisk until smooth. Stir in oil and transfer to a ziploc bag; set aside. Pour the mixture into the ice cream canister and churn following the manufacturer’s instructions until the mixture resembles the consistency of thick whipped cream. Snip the corner of the ziploc bag that the chocolate is in, and while the machine is running, slowly drizzle the chocolate into the ice cream. After chocolate is added, continue churning until the mixture resembles soft served ice cream. Transfer the ice cream to an airtight container. Cover the container and freeze the ice cream until it is firm, about 3 hours.