Cook pasta, drain, reserve 1/2 cup cooking water.
Chop and season chicken with salt and pepper.
In large skillet over high heat, cook chicken 2 tablespoons extra virgin olive oil for 8 minutes. Transfer to plate.
Cook shallots in remaining olive oil for 2 minutes. Stir in approximately 1 teaspoon flour, then wine and pasta water; simmer for 2 minutes.
Stir in sour cream, simmer 2 minutes. Add chicken, simmer one minute longer. Toss with pasta and tarragon, season with salt and pepper if desired.
Serve with nectarines and steamed broccoli.