Meanwhile, heat the remaining 3/4 cup of olive oil in the skillet. Add the chiles and sliced garlic and cook over high heat, stirring, for 2 minutes. Add the shrimp, scallions and tarragon, season with salt and pepper and cook, stirring, just until the shrimp turn pink. Add the wine and cook, stirring, for 2 minutes, then pour over the pasta and toss; add some of the cooking water if the pasta looks dry. Season with salt and pepper and serve.