This is a rich and decadent filling for our Gianduja Roulade.
Combine prunes and Armagnac in a small bowl. Cover with plastic; let soak overnight.
Heat oven to 375 degrees. Spread hazelnuts on a baking sheet. Toast until skins split, 8 to 10 minutes. Rub warm nuts in a clean kitchen towel, removing skins. Set aside.
Using a slotted spoon, transfer prunes to the bowl of a food processor. Add toasted hazelnuts and honey; pulse until finely ground. Transfer to a small bowl, and cover. Set aside at room temperature until ready to use.
Brandy or cognac can be substituted for the Armagnac.