In a large non-aluminum saucepan, whisk together ½ cup water with the Tempranillo, sugar, unsweeted cocoa powder and salt. Whisking frequently, bring to a boil and cook for one minute. Remove from the heat. Stir in the dark chocolate, whisking until melted. Stir in the vanilla extract and remaining ¾ cup water. Cool to room temperature. Transfer cooled chocolate mixture into a blender and blend for 15 seconds. Chill the mixture thoroughly in the refrigerator, approximately one hour. Once chilled, whisk briefly and pour into the bowl of an ice cream machine. Freeze the mixture in your ice cream maker, according to the manufacturer’s instructions.