Fill a large bowl with ice and water and set it aside. Bring a medium pot of filled with water to a boil. Drop the plums into the water blanch ing them until skin starts to get wrinkled, cracked and begins to peel away, 2 to 3 minutes.
Remove plums from water and immediately place them into the prepared ice bath until cool 4-5 minutes.
Remove plums from ice bath, reserving ice bath.Using your fingers gently peel the plums and cut them away from the pit in chunks.
Place the plum chunks into a medium saucepan.
Add 4 oz blackberries, wine, sugar, tarragon, triple sec and the water to the saucepan. Cover the pan, and bring to a low simmer over medium heat. Reduce heat to medium low, and allow the fruit to simmer until plums are falling apart, 15 to 20 minutes.
Remove the pan from heat and transfer the contents to a clean bowl. Then place the bowl in the reserved ice bath, stirring occasionally, until cold.
Remove tarragon sprigs from the cold mixture. Using an immersion blender puree the mixture until quite smooth and frothy.
