Preheat the oven to 375 degrees. Lightly butter a baking pan. Heat 3 tablespoons of olive oil in a skillet. Add onion and carrot, cover and cook for 10 minutes or until soft. Remove cover, add shrimp and saute for a couple of minutes just until shrimp turn pink and are firm to the touch. Remove mixture to a food processor and blend with heavy cream, lemon juice, tarragon and breadcrumbs until mixture is pureed. Season with salt and pepper. Place some stuffing on one half of each sole filet. Fold other half over the stuffing and transfer the filet to a baking dish. Drizzle remaining tablespoon of olive oil over the stuffed sole; season with salt and pepper. Bake, covered for 20 to 25 minutes or until flesh is cooked through and white and stuffing is hot.