Cook pasta; drain, reserving 1/2 cup cooking water. Season chicken; in large skillet over high, cook in 2 tbsp. EVOO, 8 minutes. Transfer to plate. Cook shallots in remaining EVOO, 2 minutes. Stir in flour, then wine and pasta water; simmer 2 minutes. Stir in creme fraiche; simmer 2 minutes. Add chicken; simmer 1 minute. Toss with pasta and tarragon; season.