1. Place prunes and Armagnac in a small saucepan to oak for at least 30 minutes, stirring occasionally.
2. Heat the soaked prunes over low heat until just warm (about 5 minutes)
3. While prunes are heating, slice foie gras into 1/2-inch slices. Heat olive oil in a small saucepan over medium heat. Quickly sauté the fois gras slices in the olive oil, cooking them no longer than 30 seconds per side.
4. Place each slice of sautéed foie gras in the center of a plate and garnish with three prunes each. Drizzle any remaining Armagnac over the foie gras.