In a non-reactive saucepan, combine the half-and-half, sugar, coconut, and salt, over medium heat and bring to a scald. Remove from the heat. Beat the egg yolks in a bowl. Add the cream mixture, about 1/4 cup at a time, to the beaten eggs, whisking in between each addition, until all is used.
Pour the mixture into a saucepan, and cook, stirring, over medium heat, for 2 to 3 minutes, or until the mixture becomes thick enough to coat the back of a spoon. Remove from the heat and cool completely.
Pour the filling into the ice cream machine and follow the manufacturer's instructions for churning time.
Combine the half-and-half and butter in a small heavy-bottomed saucepan over medium heat. Heat the mixture until a thin paper-like skin appears on the top. Do not boil. Add the chocolate and vanilla and stir until the chocolate melts and the mixture is smooth.
Remove from the heat and let cool.
The sauce can be kept refrigerated for several days, but it must be returned to room temperature before serving.
Yield: 1 1/2 cups