Line a baking sheet with parchment paper. Set aside.
Place the cream and chocolate in a medium bowl and place over a pan of barely-simmering water. Stir until the chocolate has melted and the mixture is smooth, about 6 minutes. Stir in the tarragon, wine and salt until smooth. Refrigerate for 2 hours until firm.
Let the mixture stand at room temperature until moldable, about 45 minutes. Using a melon scoop, scoop level amounts of the truffle mixture onto the prepared baking sheet. Roll into 1/2-inch balls.
Place the cocoa powder in a small bowl. Roll the truffles in the cocoa powder until coated. Arrange on a platter and serve, or refrigerate in an airtight container.