Preparation Combine chocolate and butter in medium metal bowl. Place bowl over saucepan of simmering water; stir until melted and smooth. Remove from over water. Bring cream to simmer in small saucepan; gently stir into chocolate. Add Armagnac, vanilla, and salt and stir to blend. DO AHEAD: Can be made 3 days ahead. Cool, cover, and chill. Rewarm over low heat before using.
Preparation Combine chocolate and butter in medium metal bowl. Place bowl over saucepan of simmering water; stir until melted and smooth. Remove from over water. Bring cream to simmer in small saucepan; gently stir into chocolate. Add Armagnac, vanilla, and salt and stir to blend. DO AHEAD: Can be made 3 days ahead. Cool, cover, and chill. Rewarm over low heat before using.